Modify addon with regex

I need to modify an addon to allow embeds from redgifs. You can add the code for custom websites, I need the proper code for redgifs.com

This is the addon:
https://xenforo.com/community/resources/s9e-media-sites.5973/

See attached images for example of adding the code for redgifs.com, I need proper code (my example didn't work)