Increase support for kitty enhanced keyboard protocol

[pianohacker]

Add parsing of repeat/release key events, and allow sending the CSIs to enable/disable the enhanced keyboard protocol.

See https://sw.kovidgoyal.net/kitty/keyboard-protocol/ for more information.

Note: this changes the form of the KeyEvent struct.

[TimonPost]

Interesting. Would be nice to see the modifiers like Meta implemented as well https://sw.kovidgoyal.net/kitty/keyboard-protocol/#modifiers in a followup. Lots of people commented on that and this protocol seems to allow fetching it

[pianohacker]

Agreed; I didn't want to add too much at once, but the extra modifiers would be great.

I'd also like to add support for https://sw.kovidgoyal.net/kitty/keyboard-protocol/#functional-key-definitions , but that's a weighty PR.

[pianohacker]

I ended up adding support for the functional keys, as otherwise they end up as unicode gibberish: pianohacker/crossterm@pianohacker_add_csi_u_types...pianohacker:crossterm:pianohacker_add_functional_keys

I'll create a PR for that after this one.

[TimonPost]

Looks good! Thank you so much