Update window title with video title

Clapper no longer has a title bar to show the media title during playback. Update window title so the video title is also shown on "Activities" view in addition to fullscreen top overlay.

src/widget.js

@@ -285,6 +285,7 @@ class ClapperWidget extends Gtk.Grid
                 : subtitle;
         }
 
+        this.root.title = title;
         this.revealerTop.setMediaTitle(title);
     }