Rewrite readme and update contributor docs

Incorporates #3025

.gitignore

@@ -18,3 +18,4 @@
 _rendered.rst
 /.vscode/
 /.idea/
+/spec/

CONTRIBUTING.rst

@@ -29,9 +29,7 @@ some time to complete.
 Changes to the protocol (new endpoints, ideas, etc) need to go through the
 `proposals process <https://matrix.org/docs/spec/proposals>`_. Other changes,
 such as fixing bugs, typos, or clarifying existing behaviour do not need a proposal.
-If you're not sure, visit us at `#matrix-spec:matrix.org`_
-and ask.
-
+If you're not sure, visit us at `#matrix-spec:matrix.org`_ and ask.
 
 Other changes
 ~~~~~~~~~~~~~
@@ -64,12 +62,17 @@ following:
   to fix. On the other hand, introducing new behaviour is best represented by a
   proposal.
 
+* Design or aesthetic changes, such as improving accessibility, colour schemes,
+  etc. Please check in with us at `#matrix-docs:matrix.org`_ with your proposed
+  design change before opening a PR so we can work with you on it.
+
 For such changes, please do just open a `pull request`_. If you're not sure if
 your change is covered by the above, please visit `#matrix-spec:matrix.org` and
 ask.
 
 .. _`pull request`: https://help.github.com/articles/about-pull-requests
 .. _`#matrix-spec:matrix.org`: https://matrix.to/#/#matrix-spec:matrix.org
+.. _`#matrix-docs:matrix.org`: https://matrix.to/#/#matrix-docs:matrix.org
 
 
 Adding to the changelog
@@ -100,8 +103,7 @@ the ``newsfragments`` directory. The ``type`` can be one of the following:
 
 All news fragments must have a brief summary explaining the change in the
 contents of the file. The summary must end in a full stop to be in line with
-the style guide and and formatting must be done using `Restructured Text
-<http://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html>`_.
+the style guide and and formatting must be done using Markdown.
 
 Changes that do not change the spec, such as changes to the build script, formatting,
 CSS, etc should not get a news fragment.

README.md

@@ -0,0 +1,113 @@
+# Matrix Specification
+
+This repository contains the Matrix Specification, rendered at [spec.matrix.org](http://spec.matrix.org/).
+
+Developers looking to use Matrix should join [#matrix-dev:matrix.org](http://matrix.to/#/#matrix-dev:matrix.org)
+on Matrix for help.
+
+Spec authors and proposal writers are welcome to join [#matrix-spec:matrix.org](http://matrix.to/#/#matrix-spec:matrix.org). We welcome contributions! See [CONTRIBUTING.rst](./CONTRIBUTING.rst) for details.
+
+## Structure
+
+The Matrix spec is compiled with [Hugo](https://gohugo.io/) (a static site generator) with the following structure:
+
+* `/assets`: assets that need postprocessing using [Hugo Pipes](https://gohugo.io/hugo-pipes/introduction/). 
+  For example, Sass files would go here.
+
+* `/content`: files that will become pages in the site go here. Typically these are Markdown files with some YAML front 
+  matter indicating, [among other things](https://gohugo.io/content-management/front-matter/), what layout should be 
+  applied to this page. The organization of files under `/content` determines the organization of pages in the built 
+  site.
+
+* `/data`: this can contain TOML, YAML, or JSON files. Files kept here are directly available to template code as 
+  [data objects](https://gohugo.io/templates/data-templates/), so templates don't need to load them from a file and 
+  parse them. This is also where our 
+
+* `/layouts`: this contains [Hugo templates](https://gohugo.io/templates/). Some templates define the overall layout of 
+  a page: for example, whether it has header, footer, sidebar, and so on.
+    * `/layouts/partials`: these templates can be called from other templates, so they can be used to factor out 
+      template code that's used in more than one template. An obvious example here is something like a sidebar, where 
+      several different page layouts might all include the sidebar. But also, partial templates can return values: this 
+      means they can be used like functions, that can be called by multiple templates to do some common processing.
+    * `/layouts/shortcodes`: these templates can be called directly from files in `/content`.
+
+* `/static`: static files which don't need preprocessing. JS or CSS files could live here.
+
+* `/themes`: you can use just Hugo or use it with a theme. Themes primarily provide additional templates, which are 
+  supplied in a `/themes/$theme_name/layouts` directory. You can use a theme but customise it by providing your own 
+  versions of any of the them layouts in the base `/layouts` directory. That is, if a theme provides 
+  `/themes/$theme_name/layouts/sidebar.html` and you provide `/layouts/sidebar.html`, then your version of this 
+  template will be used.
+
+It also has the following top-level file:
+
+* `config.toml`: site-wide configuration settings. Some of these are built-in and you can add your own. Config settings 
+  defined here are available in templates. All these directories above are configurable via `config.toml` settings.
+
+Additionally, the following directories may be of interest:
+
+* `/attic`: Here contains historical sections of specification and legacy drafts for the specification.
+* `/changelogs`: Various bits of changelog for the specification areas.
+* `/event-schemas`: [JSON Schema](http://json-schema.org/) definitions for the spec.
+* `/data-definitions`: Bits of structured data consumable by Matrix implementations.
+* `/meta`: Documentation relating to the spec's processes that are otherwise untracked (release instructions, etc).
+* `/scripts`: Various scripts for generating the spec.
+* `/proposals`: Matrix Spec Change (MSC) proposals. See <https://spec.matrix.org/unstable/proposals/>.
+* `/api`: [OpenAPI](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md) / Swagger definitions for
+  the spec.
+
+## Authoring changes to the spec
+
+Please read [CONTRIBUTING.rst](./CONTRIBUTING.rst) before authoring a change to the spec. Note that spec authoring takes
+place after an MSC has been accepted, not as part of a proposal itself.
+
+1. Install the extended version (often the OS default) of Hugo: <https://gohugo.io/getting-started/installing>
+2. Run `git submodule update --init --recursive` for good measure.
+3. Run `npm i` to install the dependencies. Note that this will require NodeJS to be installed.
+4. Run `npm run get-proposals` to seed the proposals data. This is not required.
+5. Run `hugo serve` to run a local webserver which builds whenever a file change is detected. If watching doesn't appear
+   to be working for you, try `hugo serve --disableFastRender` instead.
+6. Edit the specification 🙂
+
+We use a highly customized [Docsy](https://www.docsy.dev/) theme for our generated site, which uses Bootstrap and Font 
+Awesome. If you're looking at making design-related changes to the spec site, please coordinate with us in 
+[#matrix-docs:matrix.org](https://matrix.to/#/#matrix-docs:matrix.org) before opening a PR.
+
+### Windows users
+
+If you're on Windows Vista or higher, be sure that the "Symbolic Links"
+option was selected when installing Git prior to cloning this repository. If
+you're still seeing errors about files not being found it is likely because
+the symlink at ``api/client-server/definitions/event-schemas`` looks like a
+file. To correct the problem, open an Administrative/Elevated Command Prompt in your
+cloned matrix-doc directory and run the following::
+
+  cd api\client-server\definitions
+  del event-schemas
+  mklink /D event-schemas "..\..\..\event-schemas"
+
+This will delete the file and replace it with a symlink. Git should not detect
+this as a change, and you should be able to go back to building the project.
+
+## Building the specification
+
+If for some reason you're not a CI/CD system and want to render the spec yourself, follow the above steps for authoring
+changes to the specification and instead of `hugo serve` run `hugo -d "spec"` - this will generate the spec to `/spec`.
+If you'd like to serve the spec off a path instead of a domain root (eg: `/unstable`), add `--baseURL "/unstable"` to
+the `hugo -d "spec"` command.
+
+For building the swagger definitions, create a python3 virtualenv and activate it. Then run `pip install -r ./scripts/requirements.txt` and finally `python ./scripts/dump-swagger.py` to generate it to `./scripts/swagger/api-docs.json`.
+To make use of the generated file, there are a number of options:
+
+* It can be uploaded from your filesystem to an online editor/viewer such as
+  http://editor.swagger.io/
+* You can run a local HTTP server by running `./scripts/swagger-http-server.py`, and then view the documentation via an
+  online viewer; for example, at <http://petstore.swagger.io/?url=http://localhost:8000/api-docs.json>
+* You can host the swagger UI yourself. See <https://github.com/swagger-api/swagger-ui#how-to-run> for advice on how to 
+  do so.
+
+## Issue tracking
+
+Specification issues are tracked on github at <https://github.com/matrix-org/matrix-doc/issues>.
+
+See [meta/github-labels.rst](./meta/github-labels.rst) for information on what the labels mean.