New interaction type: "Reaction"

[sokunthearithmakara]

Reactions include rating, comments, and private notes + Q&A.
Close comments on a certain date.
Instructor sets rating scale with emojis.
Comments with mentions and responses (2-level).
Notification support (get notified when mentioned in a comment).
Subscription support? (optionally subscribe to get notification when there is a new comment).
Timestamp support (link comment to specific timestamp on the video).
Private notes enable learners to annotate the video.
Q&A (public or private).
Report abuse.
Report page for all reactions.
Support XP and completion tracking. Similar to forum activity, you can have students comment on the video and/or respond to comments. Set the number of comments or replies for completion tracking.