WebVTT allows additional parameters along with the line that
contains the start and end times. These were not being filtered
out while attempting to manually display captions.
This option allows developers to attach their custom handlers
before internal plyr's handlers. This should enable developers
to have full control over all the buttons including the ability
to stop event propagation if desired.
Currently, there is no simple way of acquiring media source.
This commit updates the 'source' API function to allow developers
to acquire the video source regardless of whether the video
is a youtube-embed or HTML5 video.
Future embeds just need their respective URL fetching code added
to this common function.
Guru Prasad Srinivasa