Add rel="wp-video-lightbox" in feature details url

I’m triying the following url in feature details url:
https://www.youtube.com/watch?v=a-k2gaOAQoU” rel=”wp-video-lightbox”
but when I save the link disappears or url change to
https://www.youtube.com/watch?v=a-k2gaOAQoUrel=wp-video-lightbox (then lighbox doesn’t work of course).

https://wordpress.org/plugins/features-by-woothemes/