Add video support in transcription playback

[yifeict]

希望能增加点击文本跳到视频对应位置功能，对于学习类的视频非常有意义，因为有些话是要结合ppt看才能看懂

[raivisdejus]

Translation: I hope to add the function of clicking on the text to jump to the corresponding position in the video. It is very meaningful for learning videos, because some words can only be understood by watching them in conjunction with PPT.

Development note:

• Transcript viewer does not play video, only audio, this could be improved.