wayland: support ext-background-effect-v1
This implements https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/272
KWindowSystem counterpart: frameworks/kwindowsystem!180 (merged)
Edited by Xaver Hugl
This implements https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/272
KWindowSystem counterpart: frameworks/kwindowsystem!180 (merged)