[ProofOfConcept] AutoMouseKeys layer switching

[wolfwood]

Describe your changes. Use imperative present tense.

when RelAxis x or y events occur, a timestamp is updated and if the timestamp was previously None, an F24 key Press event is injected. If a non-RelAxis event occurs more than a timeout value (750 ms right now) since the last timestamp update, an F24 key Release event is injected prior to processing the event and the timestamp is reset to None.

the expectation is that the user will map F24 to a layer-while-held action to switch to a mouse keys layer.

in a finalized version, the timeout and the key event would be configurable as part of a feature toggle.

Checklist

• Add documentation to docs/config.adoc
  • Yes or N/A
• Add example and basic docs to cfg_samples/kanata.kbd
  • Yes or N/A
• Update error messages
  • Yes or N/A
• Added tests, or did manual testing
  • Yes