Support monorepos with multiple docs plugins

[vjpr]

I am creating this issue to track all the issues related to using multiple docs plugins without a single repo.

Below is an example of my setup:

- . <- plugin-content-docs path
- .git
- tmp/logs
- .tmp/more-logs
- readme.md
- package.json
- docs <- docs for the monorepo
  - sidebar.js
  - readme.md 
- packages
  - docs-app
    - package.json
    - docusaurus.config.js 
  - pkg1 <- plugin-content-docs path
    - docs
      - sidebar.js
      - readme.md
  - pkg2 <- plugin-content-docs path
    - docs 

There are 3 docs plugins in use here. One for the monorepo root package, and two others for other packages.

I have indicated where the plugin's path config is set.

For the monorepo root docs plugin I set the path to be the root rather than the docs folder. This allows me to include the readme.md file in my docs.

Issues

• Allow custom chokidar watcher configuration
• Allow custom excludes for each content-docs-plugin's webpack mdx loader rule
• Allow referencing markdown links from the repository root

[blessanm86]

We are using docusaurus in our NX monorepo. The docs is 1 app.
It would be great if we could specify folders outside the docs app. This way we could pull the docs from other apps and libs folder.