Change hotkey overlay background and border

[aledraken]

Not sure but there doesn't seem to be anything about this in the wiki, is it even possible?

[lostinthemath]

I believe it's hardcoded, see #173

[heyoeyo]

This isn't really a direct solution, but I think passing the keybinds into fuzzel ends up being a better user experience since it makes it searchable. It also gives a lot more control over the appearance.

The only issue is that there isn't a direct way to get the keybinds from niri, though you can get close by just splitting your binds {...} section into it's own kdl file (and sending that to fuzzel), otherwise it requires parsing the config (see #3023)