Add a rofi module to the desktop group, enabled by the aggregator.
It runs the drun application launcher, bound on Super+R. A session menu
built on the same themed rofi is bound on Super+Shift+X, and every
rofi -dmenu call inherits the Stylix theme, so later utility menus
reuse it for free.
Also give layer surfaces their own fade-in (layersIn and fadeLayersIn)
a touch quicker than the window animation, so the launcher fades in
briskly rather than snapping into place.
