The original site has since been forked by other users, such as twastinfg on GitHub
It was almost certainly a of a Friday Night Funkin’ mod or the original game, hosted on GitHub Pages by a user named ggl22 (or similar). In 2021, FNF was at peak popularity, and many fans uploaded “online emulators” or modded versions so players could avoid downloading the full .exe. ggl22 github io fnf 2021
Exploring ggl22.github.io: A Snapshot of the Friday Night Funkin’ Flash Era The original site has since been forked by