Use JsonSerializer instead of Utf8Writer (#1670)

* Use JsonSerializer instead of Utf8Writer

* Rename method

src/modules/fancyzones/editor/FancyZonesEditor/DashCaseNamingPolicy.cs

@@ -0,0 +1,20 @@
+// 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.Text.Json;
+
+using FancyZonesEditor.Utils;
+
+namespace FancyZonesEditor
+{
+    public class DashCaseNamingPolicy : JsonNamingPolicy
+    {
+        public static DashCaseNamingPolicy Instance { get; } = new DashCaseNamingPolicy();
+
+        public override string ConvertName(string name)
+        {
+            return name.UpperCamelCaseToDashCase();
+        }
+    }
+}