Inserting commentator speech to stream

[akiziltoprak]

1. System ingests RTMP and SRT streams from event
2. System makes WEBRTC stream from this stream and shows it to the commentator on the web WEB.
3. Commentator sees this stream and active audio (voice) on the web page and starts to comment on the event
4. System combines original stream video and commentator's voice and generates HLS to player
5. Viewers can switch between the original audio and commentator's audio by changing audio track in the player.

[lastpeony]

I extended HlsMerger plugin to add this functionatiy. It is working fine with Hls.JS but looks like there is a bug related to this functionality in videojs and thats why its not working yet with ant media web player.

Created an issue on videojs issues

videojs/http-streaming#1556