Fix expanding the sidebar preventing hotkeys from working immediately

[hotzenklotz]

This PR fixes a bug whereby expanding/collpasing the sidebar using the little icon buttons would make the main XYZ viewports lose focs/not respond to keyboard inputs anymore. Instead of having to click in the viewport to restore focs and continue using the keyboard hotkeys this now should work without any addtional click/refocusing.

Techical details:

• It seems to me that the first blur() call only every blurred the
  element of the icon itself. For some reasons, the surround button element still retained focus/control. By also calling blur()onthe parent button element the issue resolved itself.

URL of deployed dev instance (used for testing):

• https://___.webknossos.xyz

Steps to test:

• Expand/Collapse sidebar via button
• Press any hotkey, e.g. f or SPACE, and observe that the intended behavior, e.g. movement, occurs

Issues:

• fixes Keyboard shortcuts don't work after using button to collapse/expand sidebars #5827

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(Please delete unneeded items, merge only when none are left open)

• Updated (unreleased) changelog
• Updated (unreleased) migration guide if applicable
• Updated documentation if applicable
• Adapted wk-connect if datastore API changes
• Adapted wk-libs python client if relevant API parts change
• Needs datastore update after deployment
• Ready for review

[philippotto]

thanks for digging into this!

[philippotto]

I think this blur() can be removed, as it probably doesn't do anything. As far as I know, only one blur will have an effect, since only one element can have the page focus. I also just tested it and the second blur seems to be enough to solve the issue 🎉

[philippotto]

ah, it seems like it depends on where the user clicks exactly. sometimes the inner element gets the focus and sometimes the outer element. this is why both blurs make sense (however, with a slightly differing explanation than in your PR :)).