Move documentation rendering for remaining projects to GitHub Actions

[jezdez]

Checklist

• I added a descriptive title
• I searched open requests and couldn't find a duplicate

What is the idea?

There are a few Sphinx projects that remain hosted on Anaconda's ReadTheDocs infrastructure, which has transparency and governance issues (e.g. build logs aren't visible). I'd suggest moving the docs rendering to GitHub Actions and host the docs using GitHub Pages (and point the docs.conda.io to that).

Why is this needed?

No response

What should happen?

No response

Additional Context

No response