Feature Request: Pause and resume audio and video comments #270

Audio and video comments can be stopped while they're playing, but when they are restarted, they start again from the beginning of the source. This is less than ideal for a learner who needs to pause to look something up or deal with an interruption. It would be nice let the learner pick up where they left off, rather than forcing them to restart the commentary.

I see three implementation options off the top of my head:

1. Replace the Play > Stop > Play buttons with Play > Pause > Resume. This doesn't require a UI change. It does make it harder to restart the commentary from the beginning, though. I'd guess that pausing is more desired than restarting, so I think this would still be an improvement.
2. Change the "Stop" button to a pair of buttons: Pause and Reset. The Reset button would stay visible when paused. This gives the learner more control, at the cost of a more complicated UI.
3. Replay "Stop" with "Pause", and add a progress slider. This gives the learner even more capabilities to control the playback, without complicating the UI much behind what's offered by (2). I'd imagine it's a bit more to implement this, though.

I'm sure there are other ways to handle this, too.

Ideally the TTS feature would also support this, but I don't know if that's as easy as pausing and resuming video.

I'm happy to help with an implementation, once an approach is agreed upon.