Add option to toggle captions in Canvas Studio assignments

[janraev]

Feature Request Form

Problem you are trying to address with this feature

Currently, the video player used in Hypothesis assignments using Canvas Studio content does not have a button to turn captions on/off. Captions are always turned on.

Media player in the assignment (no cc button)

Media player in Canvas Studio (with cc button)

Your solution

Include a button to toggle captions on/off.

Related ticket:
https://app.hubspot.com/contacts/6291320/record/0-5/27723690393

Slack thread:
https://hypothes-is.slack.com/archives/C01B9TRVATZ/p1754656149809669

[robertknight]

@janraev I changed the issue title to be about toggling captions rather than Canvas Studio assignments, which is I believe what was intended?