Filter out non-video id if someone pastes entire youtube URL

[profmikegreene]

Two example URLs
https://www.youtube.com/watch?time_continue=12&v=AENEbcmEp2A
https://www.youtube.com/watch?v=SLkZiILsESM

Allow the user to paste the entire youtube URL and regex the v= query parameter to get the video ID instead of erroring out.