It's disturbing that you use original developer's nickname.

Do not install this extension! This is not the original Igrigorik author! See their GitHub for confirmation.

One-starring to spread awareness that both the extension and the author of this Firefox port has no ties to the original project, as by Igrigorik's disclaimer on their Github issues page. Avoid installing/enabling since this is very suspicious behavior.

Sketchy af. The original author disavow this add-on. github.com/igrigorik/videospeed/issues/1511