Allow selecting windows

This is a bit broken right now on GNOME Shell / Mutter side,
but it should still be okay since window instrospection is
hidden behind a GSetting anyway.

obs-xdg-portal.c

@@ -551,7 +551,7 @@ select_source (obs_xdg_data *xdg)
   call = subscribe_to_signal (xdg, request_path, on_select_source_response_received_cb);
 
   g_variant_builder_init (&builder, G_VARIANT_TYPE_VARDICT);
-  g_variant_builder_add (&builder, "{sv}", "types", g_variant_new_uint32 (1));
+  g_variant_builder_add (&builder, "{sv}", "types", g_variant_new_uint32 (3));
   g_variant_builder_add (&builder, "{sv}", "multiple", g_variant_new_boolean (FALSE));
   g_variant_builder_add (&builder, "{sv}", "cursor_mode", g_variant_new_uint32 (2));
   g_variant_builder_add (&builder, "{sv}", "handle_token", g_variant_new_string (request_token));