Add MPRIS support (#25)

* Stop mpv on app close for linux/macOS (#20)

* Add initial MPRIS support

* Fix mpv path check

src/renderer/preload.d.ts

@@ -40,8 +40,10 @@ declare global {
         windowUnmaximize(): void;
       };
       localSettings: any;
+      mpris: any;
       mpvPlayer: any;
       mpvPlayerListener: any;
+      utils: any;
     };
   }
 }