Support/version for offline video playback

[AlanSixth]

It would be wonderful to extend this function to offline video playback as well, e.g. if two people have the same video files, then a similar function can be realized.

[599316527]

I created a page on which you can play local videos.

Then, coplay will works on the page if the player adapter for it is appended.

[Justineo]

I think we can provide a local page inside the extension itself to support offline videos.