video-player: Import GstPlay in Blueprint

src/components/media/video_player.blp

@@ -1,7 +1,8 @@
 using Gtk 4.0;
 using Adw 1;
+using GstPlay 1.0;
 
-$GstPlay player {
+GstPlay.Play player {
   video-renderer: $VideoPlayerRenderer video_renderer {};
 }