A document for generated functions and generalized generated functions

EDIT: the document is https://github.com/thautwarm/GeneralizedGenerated.jl/blob/master/capabilities.md

I’m working on some writing for @cscherrer 's Soss, and I think I’ve written a good document for the topics of generated functions.

I provide an example which elaborates notable performance gain and restrictions. If you still cannot understand generated functions and its use case, I do like to sell my documentation.

Also, in the next hours, in this document I’ll introduce the all restrictions I know for generated functions, and what GeneralizedGenerated.jl did to address this problem, how useful GG could be.