Expose an interface to check if a key is being pressed

[miversen33]

Is your feature request related to a problem? Please describe.
RE: Discussion #3441
I am looking for a way to indicate in the statusbar that the Caps Lock is enabled from lua. As a tangential request, it may make sense to expose a way to check if any key is currently being "activated" (pressed).

Describe the solution you'd like
There are 2 trains of thought here.

1. A function that exists (likely on window but potentially on the global wezterm object?). Something akin to

require("wezterm").is_key_pressed(SOME_KEY)
-- Or on the window object
window:is_key_pressed(SOME_KEY)

Its worth calling out that this kind of feature, while I think it would be helpful, ultimately wouldn't resolve the issue at hand as CAPS LOCK is a special stateful key (IE, CAPS LOCK is either enabled or disabled, similar to how INSERT is either enabled or disabled). Because of this, this first request is a want that could potentially be seen as its own separate work effort (and also "No" is of course acceptable).

2. A function that exists (likely on window) to check if CAPS LOCK is currently active (much more achievable IMO).

window:caps_is_active()

This would function exactly like window:leader_is_active() and I imagine under the hood the logic would be nearly the same (though leader has a timeout and caps lock generally doesn't by default).

Describe alternatives you've considered
Its possible to wrap the key in a keytable event and track the state of capslock via that but that seems really ick and not at all preferred.

Additional context
Thank you for this project :) I don't know rust in any meaningful way so I unfortunately can't really contribute at this time. Thus all I have are suggestions from an end user perspective :)

[wez]

window:keyboard_modifiers() is available now in main.

You'll need f3ee5e5 to have your update-status event handler trigger as modifiers are changed on x11 and (probably: I haven't tested it to see if actually works!) wayland.

[eugenesvk]

If you alt-tab to a different window, does the status stick for you when you switch back until you press or release a key (seems to stick here on a Mac), if so, then maybe if could check on regaining focus that no keys are held and reset the status?

[github-actions]

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