Adding in headers (#5163)

Co-authored-by: Clint Rutkas <crutkas@microsoft.com>

src/core/Microsoft.PowerToys.Settings.UI.Lib/SndShortcutGuideSettings.cs

@@ -1,4 +1,8 @@
-using System;
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
 using System.Collections.Generic;
 using System.Text;
 using System.Text.Json;