Create track event and implement support for subtitles tracks [#79469180]
Merge branch 'master' into feature/hls-subtitles

* master:
  utils.isYoutube to check filetype as well as file source [Fixes #76751170]
  Fixing comments
  if youtube video has only 1 quality and 'auto', do not show an HD toggle [Fixes #79629726]
  Fixing double-call of _onYoutubeStateChange when state changes and also removing a boolean which allowed the sendMetaEvent to be called only once without reinitializing the entire youtube provider.
First version of hls subtitles [#78853184, #79469180]
Merge pull request #174 from jwplayer/feature/hls-subtitles

Feature/hls subtitles