Major API change; adds multimedia and 3D graphics widgets. Changes: - https://gitlab.gnome.org/GNOME/gtk/-/blob/4.0.2/NEWS - https://blog.gtk.org/2020/12/16/gtk-4-0/ Co-authored-by: Jan Tojnar <jtojnar@gmail.com> Co-authored-by: Tad Fisher <tadfisher@gmail.com>