Add docs for specific helpers

[thatblindgeye]

It'd be advantageous to add some documentation for some of our more prominent helpers for contributors who don't frequent this repo as often. Essentially just including info for:

• what the helper is called
• what it's for/what it does (sentence or two)
• maybe some example code logic to show how it's most often used in the codebase
• whether it's intended to be used inline (e.g. within a node block), as a context report, or passed as a reference to the create property of the rule (e.g. renameProps)