Add ‘some modules have migrated’ disclaimer to cgit
It would be useful to add a transition message to the top of https://git.gnome.org/browse/ saying something like “GNOME is migrating to GitLab; some modules are no longer listed here and are at gitlab.gnome.org instead” — otherwise users could go to cgit and look for GLib, but be unable to find it in the main module listing, and not be sure where to look. They wouldn’t hit the redirect at https://git.gnome.org/browse/glib because the module is no longer listed on cgit.