dbus: Add internal API suitable for GlobalShortcuts
xdg-desktop-portal-gnome#47 (comment 2089569)
This adds an interface in org.gnome.Shell that provides additional functionality for managing key grabs, suitable for the GlobalShortcuts portal.
This needs mutter!3680 (merged) .
This can be controlled with https://gitlab.gnome.org/dcz/gsimpl , see instructions there.