Add window icons to titlebars

[PAI5REECHO]

To me Sway is the defacto Wayland window manager for being productive, despite this the developers don't seem to have a high priority for https://github.com/swaywm/sway/issues/4882. Perhaps this fork would be more receptive to adding this

[fluix-dev]

Yep, I'd accept a patch for this.