Override playState of mediaSession for Chrome Android

Per Google Developers official doc:

> Note: The browser may consider that the web app is not playing media
> when files are seeking or loading. You can override this behaviour by
> setting navigator.mediaSession.playbackState to "playing" or "paused".
> This comes in handy when you want to make sure your web app UI stays in
> sync with the media notification controls.

resources/assets/js/services/playback.js

@@ -93,9 +93,11 @@ export const playback = {
         this.pause()
       })
       navigator.mediaSession.setActionHandler('previoustrack', () => {
+        navigator.mediaSession.playbackState = 'playing'
         this.playPrev()
       })
       navigator.mediaSession.setActionHandler('nexttrack', () => {
+        navigator.mediaSession.playbackState = 'playing'
         this.playNext()
       })
     }