Merge pull request #2834 from mark-monteiro/add-nuget-config

Add nuget.config file

(cherry picked from commit 7731aba6f4e820f6dec3a9c3f6e852cc548245c3)
Signed-off-by: Joshua M. Boniface <joshua@boniface.me>

nuget.config

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+    <packageSources>
+        <add key="NuGet official package source" value="https://api.nuget.org/v3/index.json" />
+    </packageSources>
+</configuration>