[snake8head request] support adding video(s) to queue with a target play time

Useful for events that start at a particular time, like MMM

simple implementation just supports mass-adding the items into the queue at the target time.

more complex may add a targetTime/playAfter (or whatever) properties onto the videos so that modifications to the queue use those properties to keep the block at the same target play time, but probably overkill/unnecessary?