Layer support

[Quackdoc]

Is your feature request related to a problem? Please describe.
Some compositors like niri will tile the launcher, and other applications can go above onagre

Describe the solution you'd like
support setting as top layer on wayland

Additional context
I have done a brief search and found a crate which supports iced layers

https://github.com/waycrate/exwlshelleventloop and more specifically https://crates.io/crates/iced-layershell

[Quackdoc]

I forgot, as an alternative supporting https://gitlab.freedesktop.org/mstoeckl/windowtolayer would be nice, currently in testing it just becomes a maximized window, though this may be a issue with windowtolayer