Add doc for manifest file generated by docfx build
Add doc for manifest file generated by docfx build

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