Support layer shell

Layer shell is a wayland protocol, gtk can be done via [`gtk4-layer-shell`](https://github.com/pentamassiv/gtk4-layer-shell-gir) and qt via [`layer-shell-qt`](https://github.com/KDE/layer-shell-qt). Its like a window, without window decorations. Best for bars, launchers, widgets etc.

Layer shell qt as far as i know, not used by quickshell (a widely used application to draw widgets using qt). Quickshell uses its own implementation.

There can also be a winio layer shell implementation, see https://github.com/waycrate/exwlshelleventloop for iced related layer shell implementation.

Also https://github.com/pop-os/libcosmic as it uses layershell very much for its applets and others.

No winio files, tests, or entry points are named. Start by comparing the linked gtk4-layer-shell, layer-shell-qt, exwlshelleventloop, and libcosmic implementations with winio's existing desktop architecture. Done would require a defined API and an agreed implementation and test scope for layer-shell support.

Written by the indexing model from the issue text.