use composite markdown token aggregator. (#1889)
use composite markdown token aggregator. (#1889)


dotnet/docfx,DuncanmaMSFT/docfx,superyyrrzz/docfx,928PJY/docfx,pascalberger/docfx,dotnet/docfx,superyyrrzz/docfx,pascalberger/docfx,928PJY/docfx,superyyrrzz/docfx,hellosnow/docfx,pascalberger/docfx,hellosnow/docfx,hellosnow/docfx,dotnet/docfx,928PJY/docfx,DuncanmaMSFT/docfx