Document _includes folder

[Tomasz-Kluczkowski]

_includes folder contains reusable code - layouts and liquid code that can be treated as functions.
I would like to have a documentation for each snippet explaining what is it used for, what parameters are required, what it returns (sort of - there are no returns in liquid - it just creates a variable that then can be used in a global scope), what is the output if it produces html code out of some basic layout etc.
This is very important for other groups to have it well written.