update release note.
update release note.

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