Add current and total track numbers to metadata

app/src/main/java/org/schabi/newpipe/player/playback/BasePlayerMediaSession.java

@@ -60,6 +60,8 @@ public class BasePlayerMediaSession implements MediaSessionCallback {
         Bundle additionalMetadata = new Bundle();
         additionalMetadata.putString(MediaMetadataCompat.METADATA_KEY_ARTIST, item.getUploader());
         additionalMetadata.putLong(MediaMetadataCompat.METADATA_KEY_DURATION, item.getDuration() * 1000);
+        additionalMetadata.putLong(MediaMetadataCompat.METADATA_KEY_TRACK_NUMBER, index + 1);
+        additionalMetadata.putLong(MediaMetadataCompat.METADATA_KEY_NUM_TRACKS, player.getPlayQueue().size());
         descriptionBuilder.setExtras(additionalMetadata);
 
         final Uri thumbnailUri = Uri.parse(item.getThumbnailUrl());