List of focus ring aberrations

Summary

While working on https://github.com/pydata/pydata-sphinx-theme/pull/1549, I created a list of focus ring TODOs. I'm creating this issue to make sure that they are tracked somewhere.

[x] Sphinx Design link cards (as seen on the home page) - focus ring is broken (squished, very narrow) due to the way the link is rendered
[x] Sidebar TOC dropdown "chevron" button (does not receive focus and does not work with space or enter key)
[x] Focus ring for tabs not yet implemented
[x] Toggle (hamburger) button for left/primary mobile sidebar overlay (does not receive focus and does not work with space key or enter key). Open question: does it need to work with keyboard?
[x] Button focus rings need to be changed to match the color of the button
[x] Toggle (hamburger) button for right/secondary mobile sidebar overlay (receives focus, has focus ring, but does not respond to space or enter key). Open question: does it need to work with keyboard?
- https://github.com/pydata/pydata-sphinx-theme/pull/1585
[x] Some weird artifact for API "source" links, where a second blank focus ring appears at the end of the API method name:
- https://github.com/pydata/pydata-sphinx-theme/pull/1778
[ ] There are too many copy buttons in notebook outputs
[ ] ipyleaflet receives focus but does not show focus ring