Open .HTML file.
Find this in your code:
after('loadWorldFromGameData', function () {
hackOptions.followers.forEach(setFollower); // <-- COMMENT THIS LINE
Then do this:
Let's say you want "cat" (sprite) to be your follower.
In the cat's dialog (DLG n), add the tag: I'm a cat! I'll follow you now. (follower "cat")
The cat will now follow you.
The (follower "name") tag acts as a toggle. Calling it once starts the following; calling it again with the same name will make the sprite stop following you.
I haven't checked how followers work with exits and different rooms, though