Accessibility: Remove the "command" shortcut

[youknowriad]

The "command" shortcut to navigate to the editor's toolbar has proven to be technically difficult to implement properly without edge-cases and also have side effects. This PR removes it in favor of the alt+f10 alternative. See #2960 (comment) and #3183

If you can think of another simple shortcut, I'd be happy to add.
This also refactors the navigation to use the KeyboardShortcuts component.

Testing instructions

• Check that alt+f10 moves the focus to the header's toolbar

closes #3183

[codecov]

Codecov Report

Merging #3285 into master will increase coverage by 0.15%.
The diff coverage is 37.5%.

@@            Coverage Diff             @@
##           master    #3285      +/-   ##
==========================================
+ Coverage   31.02%   31.18%   +0.15%     
==========================================
  Files         232      232              
  Lines        6518     6504      -14     
  Branches     1163     1159       -4     
==========================================
+ Hits         2022     2028       +6     
+ Misses       3770     3755      -15     
+ Partials      726      721       -5

Impacted Files	Coverage Δ
editor/utils/dom.js	15.2% <ø> (+0.12%)	⬆️
editor/header/header-toolbar/index.js	0% <0%> (ø)	⬆️
components/keyboard-shortcuts/index.js	85.71% <100%> (+85.71%)	⬆️

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[jasmussen]

I can confirm that this works. In my case, I have the Mac keyboard set to use function keys instead of F keys, so I had to press Alt + Fn + F10, which is a super awkward key combination. But it works, which also means it works when I set MacOS to use the F keys instead of the function keys. It's also a standard, so this is a good baseline for the feature.

I understand the removal of the ⌘ key because of the technical issues it introduces. I respect that. Is there a way we can have a different command key we can use for this, in addition to Alt F10?

To be clear, if yes, we can have multiple keyboard shortcuts, totally fine to explore that in a separate PR.

[youknowriad]

yes, we can have multiple keyboard shortcuts, totally fine to explore that in a separate PR.

Yes and I'd be happy to add this to the current PR, I just don't know which shortcut to use.

[jasmussen]

Brainstorm:

• ⌘ + Shift — would this be less conflicting than just ⌘ alone?
• Alt + ⌘ — similar to above
• ⌘ ⌘ — that is, ⌘ followed by ⌘ shortly after

[aduth]

the removal of the ⌘ key because of the technical issues it introduces

To clarify, the issues I experienced in #2960 (comment) were not technical in nature.

[aduth]

Code-wise, 👍

Alt+F10 can be awkward on MacBook Pro with Touch Display since... there are no function keys 😄

[youknowriad]

Let's add another shortcut once we settle on a new one.