add comment moderation commands

[jdwit]

adds approve and hide commands for comment moderation.

usage:

ytstudio comments list VIDEO_ID --status held
ytstudio comments list VIDEO_ID --status held | jq -r '.[].id'
ytstudio comments approve COMMENT_ID [COMMENT_ID...]
ytstudio comments hide COMMENT_ID [COMMENT_ID...]

also changes comments list default output to json for pipe-friendliness.