docs(misc): Adding Documentation section to CONTRIBUTING.md (nrwl#6201)

CONTRIBUTING.md

@@ -105,6 +105,60 @@ To build Nx on Windows, you need to use WSL.
 - Run `yarn install` in WSL. Yarn will compile several dependencies. If you don't run `install` in WSL, they will be compiled for Windows.
 - Run `yarn test` and other commands in WSL.
 
+## Documentation Contributions
+
+We would love for you to contribute to our documentation as well! Please feel welcome to submit fixes or enhancements to our existing documentation pages and the `nx-dev` application in this repo.
+
+### Documentation Structure
+
+#### Documentation Pages
+
+Our documentation pages can be found within this repo under the `docs` directory. Pages that we consider framework specific are nested in their own subdirectories - otherwise they should be nested within the `docs/shared` directory.
+
+The `docs/map.json` file is considered our source of truth for our site's structure, and should be updated when adding a new page to our documentation to ensure that it is included in the documentation site. We also run automated scripts based on this `map.json` data to safeguard against common human errors that could break our site.
+
+#### Nx-Dev Application
+
+Our public `nx.dev` documentation site is a [Next.js](https://nextjs.org/) application, that can be found in the `nx-dev` directory of this repo.
+
+The `nx-dev/nx-dev/public/documentation` directory contains `.md` files that are generated from the `docs` directory when new releases are cut. As such, these should not be changed when submitting a change to existing docs.
+
+Jump to [Running the Documentation Site Locally](#running-the-documentation-site-locally) to see how to preview your changes while serving.
+
+### Changing Generated API documentation
+
+`.md` files documenting the API for our CLI (including executor and generator API docs) are generated via the corresponding `schema.json` file for the given command.
+
+After adjusting the `schema.json` file, `.md` files for these commands can be generated by running:
+
+```bash
+yarn documentation
+```
+
+This will update the corresponding contents of the `docs` directory. These are generated automatically on push (via husky) as well.
+
+Note that adjusting the `schema.json` files will also affect the CLI manuals and Nx Console behavior, in addition to adjusting the docs.
+
+### Running the Documentation Site Locally
+
+To run `nx-dev` locally, run the command:
+
+```bash
+npx nx serve nx-dev
+```
+
+You can then access the application locally at `localhost:4200`.
+
+By default, the site displays the `Latest` cut release of the docs. To see your current changes in the docs be sure to select `Preview` from the version selection box of the site.
+
+<img src="https://raw.githubusercontent.com/nrwl/nx/master/images/selecting-preview-from-version-selection-box.png" width="600" alt="Selecting Preview from Version Selection box">
+
+### PR Preview
+
+When submitting a PR, this repo will automatically generate a preview of the `nx-dev` application based on the contents of your pull request.
+
+Once the preview site is launched, a comment will automatically be added to your PR with the link your your PR's preview. To check your docs changes, make sure to select `Preview` from the version selection box of the site.
+
 ## Submission Guidelines
 
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