Support Kitty comprehensive keyboard handling

[diktomat]

When trying to map ^= and ^- to (un)stage entries, the log shows they are registered as being pressed without the control key. This being a common terminal limitation, there of course already is a fix: the comprehensive keyboard protocol pioneered by Kitty, but also supported by Wezterm, Neovim and others by now. Implementing this would, for the users of supporting terminals at least, make a whole lot of maps possible, which are not today.

[Schweber]

@Canop could you please comment on that? This would be really nice, if it's not too much trouble to integrate it.

[Canop]

This looks like a good reason to try using a newer version of crossterm, which broot doesn't use at the moment because of the big breaking changes in its data model. I'll try to see if that's possible when I find some time.