Make annotation cards focusable

[acelaya]

Closes #6306

This PR brings back the changes from #5539 and #5570, that we then had to roll back because of the issues reported in https://github.com/hypothesis/support/issues/31

However, by implementing this again I cannot reproduce any of those issues anymore. Since the event handler ignores events not targeting the card itself, it should not be triggered while editing an annotation or interacting with other child controls.

Considerations

I checked what is the role that other apps set in cards for similar use cases.
Bluesky sets link, which I think is not right for us, since our cards do not link anywhere when clicked.
Twitter sets article, which is what I set here, as it seems appropriate.
In previous attempts at fixing this issue, we set button, but I was never convinced that was the right one.

TODO

• Add tests.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.51%. Comparing base (808c294) to head (8abe5b9).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7339   +/-   ##
=======================================
  Coverage   99.51%   99.51%           
=======================================
  Files         271      271           
  Lines       10977    10983    +6     
  Branches     2621     2625    +4     
=======================================
+ Hits        10924    10930    +6     
  Misses         53       53           

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