How do I get local storage extension to run in an embed of a packaged project (plain html file)?

[SiIentNinja]

Question in title

This is probably a stupid question, but I have very little coding experience outside of Scratch. I'm not sure if it is even possible.

Not sure where if this is the correct place to ask this? If you know a better place to ask, please tell me.
It doesn't say who made the extension in extensions.turbowarp.org.

Help is greatly appreciated :)