Add EF6 to the list of daily build feeds (#12473)

Author: divega

docs/DailyBuilds.md

@@ -16,6 +16,7 @@ If you want to download the latest daily build and use it in a project, then you
           <add key="dotnet-core" value="https://dotnetfeed.blob.core.windows.net/dotnet-core/index.json" />
           <add key="extensions" value="https://dotnetfeed.blob.core.windows.net/aspnet-extensions/index.json" />
           <add key="entityframeworkcore" value="https://dotnetfeed.blob.core.windows.net/aspnet-entityframeworkcore/index.json" />
+          <add key="entityframework6" value="https://dotnetfeed.blob.core.windows.net/aspnet-entityframework6/index.json" />
           <add key="aspnetcore-tooling" value="https://dotnetfeed.blob.core.windows.net/aspnet-aspnetcore-tooling/index.json" />
           <add key="aspnetcore" value="https://dotnetfeed.blob.core.windows.net/aspnet-aspnetcore/index.json" />
           <add key="aspnet-blazor" value="https://dotnetfeed.blob.core.windows.net/aspnet-blazor/index.json" />