syncplay: add assistant to maintainers

pkgs/applications/networking/syncplay/default.nix

···
     description = "Free software that synchronises media players";
     license = licenses.asl20;
     platforms = platforms.linux ++ platforms.darwin;
-    maintainers = with maintainers; [ Enzime ];
+    maintainers = with maintainers; [ assistant Enzime ];
   };
 }