Promote Youtube Center's new feature (which clones this script).
Hook into the `appbar-guide-delay-load` event, as it's called much. It
should be called on every single page however, unlike the other
events...

Fix another regression from rewriting the script: check if the script
is on a /watch? page before runnning.
Add description for 1.35
Removed accidental [Dev] on the script name that got leftover.