Followup of #23876 according to my unreleased review demanding tooltips.
Additionally
- add a `muted` equivalent for buttons
- convert `switch to legacy` to an actual button
- enroll `switch to legacy` in the builtin pseudo focus cycle
- remove spaces between the buttons
The effect of the `muted` class is what you would expect: The button
loses all of its normal styling, and is defined only by its content instead.
This will help reduce a11y infractions in the future, as that was one of
the major points why people didn't use `<button>` tags and decided on a
bad fix (i.e. through `<div>`s) instead.
## Appearance
![image](https://user-images.githubusercontent.com/51889757/229510842-337378e5-faa5-4886-a910-08614c0c233d.png)
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Co-authored-by: silverwind <me@silverwind.io>
The completion popup now behaves now much more as expected than before
for the raw textarea:
- You can press <kbd>Tab</kbd> or <kbd>Enter</kbd> once the completion
popup is open to accept the selected item
- The menu does not close automatically when moving the cursor
- When you delete text, previously correct suggestions are shown again
- If you delete all text until the opening char (`@` or `:`) after
applying a suggestion, the popup reappears again
- Menu UI has been improved
<img width="278" alt="Screenshot 2023-04-07 at 19 43 42"
src="https://user-images.githubusercontent.com/115237/230653601-d6517b9f-0988-445e-aa57-5ebfaf5039f3.png">