Replay button functionality for exp-lookit-video

For the exp-lookit-video frame, there is no option for a replay button for participants. You can only set a video to automatically replay or loop, and there is no replay option in the video controls. I believe participants could scrub back on the video in the video controls by manually clicking, but this is not something that is apparent/accessible to most families.

It would be great to add a replay button option for the video, like for audio in the exp-lookit-images-audio frame! Implementing this the exact same way as the exp-lookit-images-audio frame in the JSON parameters and resulting UI would make this intuitive and consistent for both researchers and families.

Compare the exp-lookit-video frame with the exp-lookit-images-audio frame, focusing on the JSON parameters and resulting UI for replay controls. Add equivalent replay-button behavior for video and verify that participants can use it while researchers can configure it consistently.

Written by the indexing model from the issue text.