Create NuGet.config for blob feed publishing (#2199)

Author: ViktorHofer

src/package/publish/NuGet.config

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+ <fallbackPackageFolders>
+ <clear />
+ </fallbackPackageFolders>
+ <packageSources>
+ <clear/>
+ <add key="central blob feed" value="https://dotnetfeed.blob.core.windows.net/dotnet-core/index.json" />
+ </packageSources>
+</configuration>