Change the name of the NuGet source

Use `nuget` instead of `nuget.org`, which matches the config file created with `dotnet new nugetconfig`

Author: 0xced

NuGet.config

@@ -2,6 +2,6 @@
 <configuration>
   <packageSources>
     <clear />
-    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
+    <add key="nuget" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
   </packageSources>
 </configuration>