Will there absolutely positively never be any GTK+ 3.23/24 releases?
After all these years of not adding API, or deprecating API, in micro
releases, I feel very uneasy about doing that in gtkmm 3.22.* just
because GTK+ seems to be doing it.
But if there will never be a GTK+ 3.24, we could have a gtkmm 3.24 that
adds and deprecates API without causing too much confusion in the
future.