[Feature Request] Expose subtitle text through the VideoPlayerController extension

[dariyooo]

Hi, thank you for this amazing package.
I'm using fvp as the video_player backend and I'd like to draw the embedded subtitles myself in Flutter (I want to apply custom styling etc to them) instead of having mdk render them onto the video.

Problem is I can't get the actual subtitle text from VideoPlayerController. getMediaInfo() only gives me the stream metadata, and onSubtitleText lives on mdk.Player, which I don't have access to unless I ditch VideoPlayerController entirely.
Any chance onSubtitleText could be exposed on the FVPControllerExtensions? Something like:

void onSubtitleText(void Function(double start, double end, List<String> texts) cb);

Would let me keep using video_player and still get the cues. Thanks!

[wang-bin]

try master branch