update release note
update release note

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