Backport EventController*s that GTK has backported from master to gtk-3-24
EventControllerScroll, EventControllerMotion, and EventControllerKey were backported to gtk-3-24 but did not land in gtkmm-3-24. Can they still be added now in gtkmm-3-24? It would be a shame to miss out on these in gtkmm; including them would encourage using recommended ways of handling events and ease migration to version 4.
There's also GtkPadController, but we never seem to have wrapped that, even in master.