Documentation

Some docs based on jsx's docs.

I added the new exports `apply` and `patch` and updated `test`, although i didnt check the other commits intensively in this docs, but this way you can have a good baseline doc structure.

The export function explanations arent as in depth as jsx's explanations.

Let me know if there's anything you'd like me to change or go more in-depth with; i'm not really a good erlang-er yet so i may not explain it adequately... but im working on getting more experience and contributing more to the community so I'll do what i can :smile: