Allow VoidSymbol keycode to be seen by wezterm

[digitallyserviced]

When using setxkbmap to disable the functionality of CapsLock, it shows as 0x00FFFFFF VoidSymbol keycode. That was not being picked up by wezterm.

These changes allow it to be picked up as VoidSymbol so the CapsLock key can be used without any unintended side-effects.

This is how xev and other applications see it once disabled and could even be used when disabling other keys to have them be used similarly.

Makes for a great LEADER independent from anything else without going shift crazy.

[wez]

Thanks for this! What do you think about not including void symbol at the terminal layer? There's no way to encode that concept in terminal input/output, so it doesn't seem necessary.

[wez]

Please also cargo fmt and update the PR to make the CI happy!

[digitallyserviced]

I think I cleaned up the unnecessary KeyCodes so that only where it needs to be added for key events and bindings are in there. Also cargo fmt and re-tested.

[wez]

Thanks!