README: Include some documentation about the main configuration properties
README: Include some documentation about the main configuration properties

This documents the main blocks and some of their properties. It doesn't document
every single configuration property, instead provides guidance to find and
understand them by looking at the presets.

Ref #157

stutrek/esformatter,Flet/esformatter,royriojas/esformatter,uiureo/esformatter,leftstick/esformatter,sakabako/esformatter,millermedeiros/esformatter,mwdg/esformatter,glifchits/esformatter,TommyM/esformatter,wbinnssmith/esformatter