minor update on cross reference spec
minor update on cross reference spec

dotnet/docfx,dotnet/docfx,LordZoltan/docfx,superyyrrzz/docfx,hellosnow/docfx,928PJY/docfx,superyyrrzz/docfx,pascalberger/docfx,dotnet/docfx,sergey-vershinin/docfx,hellosnow/docfx,pascalberger/docfx,superyyrrzz/docfx,DuncanmaMSFT/docfx,hellosnow/docfx,LordZoltan/docfx,LordZoltan/docfx,928PJY/docfx,928PJY/docfx,LordZoltan/docfx,sergey-vershinin/docfx,sergey-vershinin/docfx,DuncanmaMSFT/docfx,pascalberger/docfx