[Request] Mark as seen

[Bugallow]

I have a pretty sizable library, so it'd be nice for Voracious to highlight the videos I've seen so I know where I left. A small "recently watched" message might also do the trick.

[artemmezh]

It is feature have already done in this branch https://github.com/artemmezh/voracious/tree/ankiConnect-fix-new-version