Check for keyboard accessibility

[mary-ext]

Tracking issue for checking keyboard accessibility, if I see any I'll point it out here before filing individual ones as necessary.

Tasks

Preview Give feedback

1. Log out button on the sidebar can't be focused
2. Search button on the sidebar can't be focused (I think we should, just to have another way that isn't with Ctrl+K)
3. Checkboxes don't have focus ring, notable examples include table selections
4. Color picker doesn't have focus ring
5. Can't focus on color picker presets
6. Action button ring focus might not be very obvious (we should probably give this an outline)
7. Can't copy JSON viewer contents to clipboard