Add docs for installing on windows and linux
Add docs for installing on windows and linux

ajhager/engi,Newbrict/engo,Newbrict/engi,EtienneBruines/engi,guregu/eng,EngoEngine/engo,wangshijin/engi,mboersma/engi,Newbrict/engi,Newbrict/engo,guregu/engi,paked/engi,EngoEngine/engo