Organize docs in docs folder

[bernars-usa]

The documentation in https://github.com/usds/us-forms-system/tree/master/docs is accurate (according to people in our kickoff meeting!), but now needs some organization, such as some directory-level README.md files for navigation, and likely breaking up some information into separate files.

I'll read through what exists and put together an outline, solicit feedback on the organization, then open some PRs. 📚

cc @usds/forms-system

[bernars-usa]

Here's a first crack at an outline based on what I've found in https://github.com/usds/us-forms-system/tree/master/docs. I'm likely mixing up terminology or order of importance... just point it out and I'll move/fix.

🗺 denotes a "map topic", which is a high-level conceptual topic that collects related topics together.

Topic Title	Source
🗺Getting Started with the Forms System Library	getting-started.md
Creating a new application with the US Forms System Starter App	getting-started.md#1-start-a-new-application
Installing the library in an existing application	getting-started.md#2-install-in-an-existing-application
🗺Building a form	NA
About the JSON schema standard and react-jsonschema-form	walkthrough.md#json-schema, walkthrough.md#how-react-jsonschema-form-works
Creating a form config file	form-config.md#form-config, form-config.md#uischema-configuration
Adding widgets	field-library.md#widgets
Adding widget definitions	field-library.md#definitions
Creating custom widgets	walkthrough.md#customization, form-config.md#uischema-configuration
Creating multi-page forms	walkthrough.md#multi-page-forms
🗺Form recipes	form-config.md#schemaform-cookbook
Writing custom field validation	form-config.md#i-need-to-write-custom-validation
Validating a field based on other fields in the same object	form-config.md#i-need-to-validate-a-field-based-on-other-fields-in-the-same-object
Changing drop-down options based on data in another field	form-config.md#i-want-to-change-the-options-of-a-dropdown-based-on-some-other-field-data
Creating a block of text with no associated fields	form-config.md#i-want-to-show-a-block-of-text-without-any-fields
Conditionally hiding a group of fields	form-config.md#i-want-to-conditionally-hide-a-group-of-fields
Styling expanded or collapsed fields	form-config.md#i-want-to-indent-or-style-the-fields-that-are-using-expandunder
Conditionally including a page	form-config.md#i-want-to-skip--conditionally-include-a-page-based-on-some-information

[bernars-usa]

WIP PR opened in #90.

[annekainicUSDS]

The outline looks great! In looking through some of the docs I'm noticing a bunch of things that need updating, but we can dig into the content once they are reorganized.

[bernars-usa]

I'm noticing a bunch of things that need updating, but we can dig into the content once they are reorganized.

Definitely. 👍 Thanks for reviewing, @annekainicUSDS!

[bernars-usa]

Getting Started content PR is ready for review: #96.