Its a skript addon which adds so much to the skript plugin. The futures are listed in the website which shows all of the futures for most skript addons https://docs.skunity.com/syntax/search/addon:SharpSK
The Spigot Page for SharpSK
https://www.spigotmc.org/resources/sharpsk-fork-1-16-4-new-update.87707/
Thanks!