Phase 2: Migrate CodeConverterPackage to include Extension contribution

Author: GrahamTheCoder

Vsix/CodeConverterPackage.cs

@@ -5,6 +5,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.VisualStudio.ComponentModelHost;
+using Microsoft.VisualStudio.Extensibility;
 using Microsoft.VisualStudio.LanguageServices;
 using Microsoft.VisualStudio.Shell;
 using Microsoft.VisualStudio.Threading;