Docs: add ref to env.host and env.roledefs
Docs: add ref to env.host and env.roledefs

For intersphinx linking

cmattoon/fabric,qinrong/fabric,sdelements/fabric,kxxoling/fabric,amaniak/fabric,jaraco/fabric,itoed/fabric,ploxiln/fabric,mathiasertl/fabric,fernandezcuesta/fabric,pgroudas/fabric,TarasRudnyk/fabric,tekapo/fabric,tolbkni/fabric,rodrigc/fabric,bspink/fabric,askulkarni2/fabric,opavader/fabric,xLegoz/fabric,rane-hs/fabric-py3,bitmonk/fabric,elijah513/fabric,SamuelMarks/fabric,cgvarela/fabric,rbramwell/fabric,likesxuqiang/fabric,haridsv/fabric,raimon49/fabric,kmonsoor/fabric