Got the idea when I saw https://www.youtube.com/watch?v=3tK06u22VQg
Allows whitelist to be enabled in Singleplayer worlds.
This is useful for only allowing your friends (who hopefully aren't griefers) to join your lan worlds, with mods like e4mc.
Just use the /whitelist command, which works exactly like the vanilla one!
The whitelist.json and enabled.json ('cause there's no server.properties on singleplayer) are stored in the world folder in lan-whitelist.