per-monitor work areas
If window manager supports _NET_WORKAREAS use per-monitor work areas.
https://mail.gnome.org/archives/wm-spec-list/2018-December/msg00000.html
https://gitlab.freedesktop.org/xdg/xdg-specs/merge_requests/22
See also mutter!370 (merged)
Fixes #980 (closed) and #1086 (closed)
Edited by Alberts Muktupāvels