[Gtk] add support for Maui - Resources

[lytico]

issue

it is unclear how Maui Resources should be handled:

https://github.com/lytico/maui/blob/08f1f616c11aba01cce049f2659616838b2b9382/src/Controls/samples/Controls.Sample/Maui.Controls.Sample.csproj#L84-L89

are they just plain Assembly.GetManifestResourceStream ?

maybe a misleading hint:

there is a Gkt-Resource-Handling:

https://docs.gtk.org/gio/struct.Resource.html