chore: update contributing guide (software-mansion#2140)

## Description

Our contributing guide was very basic and written long time ago. I
updated it with some more insights and details on how to start
contributing to this project.

---------

Co-authored-by: Tymoteusz Boba <Tymoteusz.Boba@gmail.com>
Co-authored-by: Kacper Kafara <kacper.kafara@swmansion.com>

guides/CONTRIBUTING.md

@@ -1,11 +1,9 @@
-# Contributing to `react-native-screens`
+# Contributing to react-native-screens
 
-### Welcome
+## Welcome!
 
 Thank you for considering contributing to `react-native-screens`. It's people like you that make open source projects thrive! We love to receive contributions from our community and there are many ways for *you* to be a part of this. 
 
-_tl;dr **Please** do not ignore templates for issues and pull requests and everything will be fine_
-
 ### Found a bug?
 
 If you’ve encountered a bug, don't hesitate to submit [an issue](https://github.com/software-mansion/react-native-screens/issues). Just check if someone didn't report it lately.
@@ -18,26 +16,165 @@ When filing an issue, make sure to provide:
 - **snippet of code or Snack that reproduces the bug**. Check out [this guide](https://stackoverflow.com/help/minimal-reproducible-example)
 - version of `react-native` and `react-native-screens` 
 
+### Got a question or an idea for a feature?
+
+We use GitHub issues exclusively for tracking bugs. For questions and feature requests check out [Discussions](https://github.com/software-mansion/react-native-screens/discussions).
+
 We've provided a template on GitHub that simplifies the process of filing an issue.
 
 Following these few steps will show great respect for the time of the developers managing and developing this open-source project.
 
 We inform you that unrespectful issues will be closed.
 
-### Got a question or an idea for a feature?
+## Ways to Contribute
 
-We use GitHub issues exclusively for tracking bugs. For questions and feature requests check out [Discussions](https://github.com/software-mansion/react-native-screens/discussions).
+1. **Replying and handling open issues** – great way to contribute without writing a single line of code is triaging the issues. We often get issues that have generic errors, occur only in very specific cases, do not have proper example or reproducible repository. One way to help is preparing and filling those details, which will help other contributors get up to speed with the issue faster. 
+
+2. **Reviewing pull requests** – reviewing Pull Requests is crucial as it may help catch the corner cases or bugs that the developer did not notice. Every review matters as it may help polish quality of the library.
+
+3. **Contributing to Code** – code-level contributions generally come in the form of pull requests. By contributing to code you help us with solving issues, fixing bugs or introducing new amazing features. If you want to start your adventure with open source it's good idea to take a look at [good first issue](https://github.com/software-mansion/react-native-screens/pulls?q=is%3Apr+is%3Aopen+label%3A%22good+first+issue%22) on GitHub. Read more about [contributing to code](#contributing-to-code). 
+
+### Repository overview 
+
+- `android` – source code of native implementation for Android
+- `common` – C++ code related to components - shadow nodes and state
+- `cpp` – C++ code for turbo modules
+- `apps` – apps implementations shared by wrappers
+- `Example` – paper version of React Native mobile example app from apps/examples
+- `FabricExample` – fabric version of React Native mobile example app from apps/examples
+- `FabricTestExample` – fabric version of React Native mobile app containing test examples from apps/test-examples
+- `gesture-handler` – interop between react-native-screens and react-native-gesture-handler
+- `guides` – guides for developers
+- `ios` – source code of native implementation for iOS
+- `native-stack` – description of native stack v5, actual implementation can be found in `src/native-stack`, this will be deprecated in favor of react-navigation in near feature
+- `react-navigation` – git submodule that refers to the react-navigation repository. Used mainly to test changes for newer versions of native stack.
+- `reanimated` – interop between react-native-screens and react-native-reanimated
+- `scripts` – utility scripts, used by CLI
+- `src` – library TS core code 
+- `TestsExample` – paper version of React Native mobile app containing test examples from apps/test-examples
+- `TVOSExample` – React Native example app for TVOS
+- `windows` – source code of native implementation for Windows
+
+## Handling open issues 
+
+Often understanding and reproducing the problem can be very time consuming task. The great way to help other contributors get up to the speed with solving an issue is providing detailed description and *reproducible* example. The GitHub already has a template for creating issue, nevertheless we still encounter issues that do not have all necessary details, like:
+
+- repository that we can clone and quickly see the problem,
+- very generic reproduction steps,
+- missing description,
+- not related or truncated stack trace. 
+
+What you can do is ask the owner of an issue for such details or try provide them by yourself - try to reproduce the problem and provide missing details, so other developer can start debugging straightaway! 🎉
+
+## Contributing to Code
+
+Submitting Pull Requests that resolve issues is great way to contribute to Screens. If you eager to start contributing right away, we have list of [good first issues](https://github.com/software-mansion/react-native-screens/pulls?q=is%3Apr+is%3Aopen+label%3A%22good+first+issue%22) that contain bugs which have limited scope. In this section we'll describe in more details how to play around with react-native-screens setup. 
+
+> [!tip]
+> For commits and pull request names we follow a [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) specification.
+
+We have two types of applications: pure examples (Example, FabricExample as wrappers and apps/examples for source code) and examples, dedicated for tests from issues / pull requests (FabricTestExample, TestsExample as wrappers and apps/test-examples for source code). The first work as a showcase of the library, the latter contains specific test cases that corresponds to GitHub issues. For example, `Test1864.tsx` corresponds to issue [#1864](https://github.com/software-mansion/react-native-screens/issues/1864). Our developer flow usually consists of creating new `Test*.tsx` file with code example that we try to fix or add. For new features we try to prepare showcases in Example app.  
+
+- `apps/examples` – source code with showcase app
+- `apps/test-examples` – source code with test examples app 
+- `Example/src` – wrapper with paper architecture for examples app
+- `TestsExample/src` – wrapper with paper architecture for test examples app
+- `FabricExample/src` – wrapper with fabric architecture for examples app
+- `FabricTestExample/src` –  wrapper with fabric architecture for test examples app
+- `TVOSExample/src` – source code with example app for TVOS
+- `src` – contains JS core code of the library
+- `android` – source code related to Android native part
+- `ios` – source code related to iOS native part
+
+### Working on Android
+
+To begin with, let install all dependencies:
+
+1. `yarn`
+2. `yarn submodules`
+3. `(cd apps/test-examples && yarn)`
+4. `(cd react-navigation && yarn prepare)`
+5. `cd TestsExample`
+6. `yarn`
+7. `yarn start` – make sure to start metro bundler before building the app in Android Studio
+
+and open `react-native-screens/TestsExample/android` with Android Studio.
+
+![Android Studio](android_studio.png)
+
+The native source code of react-native-screens can be found in `react-native-screens` module, in `kotlin+java/com.swmansion.rnscreens` (ensuring your project view is in the `Android` mode). Making sure metro builder is run, you can now build React Native app or debug native code. 
+
+### Working on iOS
+
+To begin with, let install all dependencies:
+
+1. `yarn`
+2. `yarn submodules`
+3. `(cd apps/test-examples && yarn)`
+4. `(cd react-navigation && yarn prepare)`
+5. `cd TestsExample`
+6. `yarn`
+7. `(cd ios && pod install)`
+8. `yarn start` – make sure to start metro bundler before building the app in XCode.
+
+and open `react-native-screens/TestsExample/ios/TestsExample.xcworkspace` with XCode.
+
+![XCode](xcode.png)
+
+To find the native source code of `react-native-screens` navigate to `Pods > Development Pods >  RNScreens > TestsExample > node_modules > react-native-screens > ios` or `Pods > Development Pods > RNScreens > .. > TestsExample > node_modules > react-native-screens > ios`. Making sure metro builder is run, you can now build React Native app or debug native code. 
+
+### Fabric 
+
+Codegen introduced by the [new architecture](https://github.com/reactwg/react-native-new-architecture/blob/main/docs/codegen.md) is fired automatically for iOS while runing `pod install` or when runing `FabricExample` in Android Studio. Developer can also run it manually by going into `./FabricExample/android` and running `./gradlew generateCodegenArtifactsFromSchema`. In both cases it is important to copy changed files from `/android/build/generated/source/codegen/java/com/facebook/react/viewmanagers/` to `android/src/paper/java/com/facebook/react/viewmanagers/`, so the interfaces are in sync for Paper architecture. 
+
+### Preparing Pull Request
+
+When your code changes are ready, it is time to open your Pull Request. GitHub already has a template that helps you properly post your changes. The most crucial are:
+
+1. **Description**:
+ - If you're solving specific issue, start with linking it.
+ - Write what are your motivations. 
+2. **Changes** - write what you have changes and why.
+3. **Screenshots / GIFs** – if applicable it's great idea to attach screen or video before and after changes.
+4. **Test code and steps to reproduce** – describe how others can test your change, if you didn't add `Test*.tsx` file it's good idea to add code snippets here. 
+
+### Do I need to prepare Pull Request for react-navigation too? 
+
+Currently, native stack is both in `react-native-screens` and `react-navigation`. `react-native-screens` contains native-stack v5 (`src/native-stack`), newer versions (v6, v7) are moved to `react-navigation` (available on branches `main`, `6.x`), hence in some cases it is necessary to prepare a pull request for `react-navigation` alongside the `react-native-screens` changes. 
+
+> [!CAUTION]
+> Currently, in this setup we have some code duplications that we're aware of. We're planning to deprecate native-stack v5 soon and remove it from react-native-screens.
+
+#### Changes in native code 
+
+If your change is only related to the native code (for example you're fixing a bug), you **do not need** to create a PR in the `react-navigation` repository. `react-native-screens` is a separate library installed alongside `react-navigation`, so you can just increase version of `react-native-screens` in your package.json file.
+
+#### Changes in JS code or both
+
+If you're changing native-stack v5 (`src/native-stack`) you **do not need** to create a PR in the `react-navigation` repository.
+
+If you're changing native-stack v6, v7 you **need to** create a PR in the `react-navigation` repository, since the code belongs there now.
 
-### Pull requests
+If you're changing core functionality:
+- If it's a bug fix and does not change the interface, then you **do not need** to create a PR in `react-navigation` repository.
+- If you're adding a new feature or changing API, you **need to** create a PR in `react-navigation` repository, that exposes new changes.
 
-Pull requests are more than welcome 🚀
+> [!TIP]
+> As the rule of thumb, if you're changing the public interface, you need to open PRs to the `react-navigation` repository.
 
-We've created a template to help you with the process of submitting a pull request to this project. Remember to change or add documentation as needed and provide a code snippet (preferably added to `TestsExample/` project) that the developers could test your change on. In the PR template we've added a checklist for all the places where the documentation should be updated.
+### What is the flow to integrate with react-navigation
 
-If it's your first pull request [this guide](https://github.com/MarcDiethelm/contributing/blob/master/README.md) might be helpful for you.
+When you propose the changes that require creating a PR to the `react-navigation` repository, please follow these steps:
 
-### Naming convensions
+1. Create a PR with `react-native-screens` changes
+2. Create a PR with changes for native-stack in `react-navigation`
+3. Wait for both to pass the review and have all checks passed
+4. Merge `react-native-screens` changes
+5. Merge `react-navigation` changes
+6. Upgrade the version of main branch index reference in `react-native-screens` (usually, git checkout on a submodule should be sufficient)
+7. Post and merge ASAP upgrade of the main branch reference of `react-navigation`
 
-For commits and pull request names we follow a [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) specification.
+> [!WARNING]
+> Those steps are crucial, since changing the API in react-native-screens without merging react-navigation changes may cause both libraries going out of sync and crashing (i.e. because of not existing property). On the other hand, if you don't perform step 6 and 7, test examples and showcase app may stop working in react-native-screens.
 
-For branch names we use `@username/description-separated-by-dashes` convention.
+See you on GitHub! 🎉