frontend: Finish interactivity

src/MediaPlayer.ts

@@ -96,6 +96,10 @@ export class MediaPlayer {
         return this.modify(() => this.writeCommand("playlist-next", []));
     }
 
+    public async skipTo(index: number) {
+        return this.modify(() => this.writeCommand("playlist-play-index", [index]));
+    }
+
     public async previous() {
         return this.modify(() => this.writeCommand("playlist-prev", []));
     }