Add an xkb layout monitor to otter-shell

Something like https://github.com/drougas/xkb-monitor (I used it on Waybar and you may be able to use it here since it's supposed to work on all Wayland compositors) or https://docs.noctalia.dev/noctalia/bar/widgets/keyboard-layout/ -- an additional popup notification when the layout is changed, like noctalia has, would be grand.

I use three languages with different alphabets for work and school, and I know there are other folks here who swap between two or more languages as well.