Improve edx-platform docs and discoverability

[robrap]

This is a follow-up to #33327, which made app-level docs part of the edx-platform readthedocs output.

Improvement ideas:

• Add app-level READMEs
• Add top-level index page(s) to make discovery of app-level docs easier.
  • An ADR index page would be nice. It is very difficult to find the ADRs.
• Eventually update OEP-19 with best practices for exposing these for a repo based on experience with edx-platform.

[farhan]

OEO-19 doc

[farhan]

@robrap We need the further details on the story:

Add app-level READMEs

1. What content will we add in the readme?
2. Will we add links of all the docs available inside the app on the read me page for easy access?

For reference:
There is a PR in which we have already linked all the django-app docs to https://docs.openedx.org/
#34462

[FuaadZam]

@feanil Reminder on open questions form Farhan.

[feanil]

@farhan a lot of apps already have readmes and I think Robert is suggesting that these should also be included in the docs and serve as a top level page for the other docs in the djangoapp.

[robrap]

I'll give some links for my points.

• Add app-level READMEs

• Here is an example README in github: https://github.com/openedx/openedx-platform/blob/master/lms/djangoapps/courseware/README.rst
• Here are the docs for the same djangoapp: https://docs.openedx.org/projects/edx-platform/en/latest/references/docs/lms/djangoapps/courseware/index.html
• Note that the README does not appear in readthedocs.

• Add top-level index page(s) to make discovery of app-level docs easier.
  • An ADR index page would be nice. It is very difficult to find the ADRs.

Looking at the same docs.openedx.org link above, notice the left-hand nav. Someone needs to literally expand the whole tree to find out where there are useful docs, or whether or not there are any docs for a given app. One or two index pages would make this quicker to scan without clicking.