Template Engine CLI commands: separate definitions from implementations

Author: tmat

src/Cli/Microsoft.TemplateEngine.Cli/CommandDefinitions/CollectionExtensions.cs

@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.TemplateEngine.Cli;
+
+internal static class CollectionExtensions
+{
+    public static void AddRange<T>(this ICollection<T> collection, IEnumerable<T> items)
+    {
+        foreach (T item in items)
+        {
+            collection.Add(item);
+        }
+    }
+}