Add ability to mark show as watched or unwatched

[RyanEwen]

Hi there,

This is probably pretty niche, but I would love to be able to toggle things as watched or unwatched.

I use this integration to play Futurama every night for background noise. It's a simple play futurama command. However, once the series has been marked as watched, we need to manually mark the series as unwatched in order to start going through it again. Otherwise it starts at episode one every night.

Cheers

[demonspork]

This could also be accomplished by using on deck instead of just finding first unwatched. Not sure if the API has a way to do that.