Add NuGet.config

NuGet.config

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <add key="NUNit MyGet Feed" value="https://www.myget.org/F/nunit/api/v2" />
+    <add key="nuget.org" value="https://www.nuget.org/api/v2/" />
+    <add key="api.nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
+  </packageSources>
+</configuration>