We need this in the main gnome-shell executable in order to locate
the private Shell and St typelibs, but those aren't useful or even
usable in the extension-prefs/portal helper tools.
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/192
Add a small DBus-activated GtkApplication that embeds a WebKitWebView
and implements some minimal logic to see if the login succeeds.
It will try to connect to a custom NM-provided url (the portal login
page), if one exists, or to www.gnome.org in the normal case of
a portal doing redirect.
https://bugzilla.gnome.org/show_bug.cgi?id=704416