An angel can help me to find this pvp addon plz (rogue)

I saw this addon in a video of duels between rogues but I never found it :(

addon: https://imgur.com/lzvf70r

video https://www.youtube.com/watch?v=qwhzQVSxdZQ

SpellAlerter: https://www.curseforge.com/wow/addon...ownload/406635