Feature proposal: add a filter on the README.md page

## What are the schemas that are affected by the issue

There are many "deprecated" entries.
A filter to toggle/show only _stable_ or _experimental_ or _deprecated_ entries would make the document more accessible.

Start by reading README.md and cataloging how entries are marked as stable, experimental, or deprecated. Determine how a reader could toggle those categories without losing access to the other entries; done means the README provides working filters for all three statuses and remains accessible.

Written by the indexing model from the issue text.