API Documentation in README (#3904)

* Documentation

* immutable types / textEditor is a render function

* nit

* remove return types from titles

* fix incorrect generics

* nit

* tweaks

* tweak

* add missing imports

* tweak

* more tweaks

* tweaks

* tweaks

* add some performance notes

* remove ref line

* add links

* Update README.md

Co-authored-by: Aman Mahajan <amahajan@stratag.com>

---------

Co-authored-by: Aman Mahajan <amahajan@stratag.com>

Author: nstepien