Add nuget.config to configure package sources

(cherry picked from commit 6f88706d420abd1a867c71b30a7594df6f4756e3)

Source/nuget.config

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+    <packageSources>
+        <clear />
+        <add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
+    </packageSources>
+</configuration>