Use JsonSerializer instead of Utf8Writer (#1670)

* Use JsonSerializer instead of Utf8Writer

* Rename method

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

@@ -0,0 +1,22 @@
+// 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.Linq;
+
+namespace FancyZonesEditor.Utils
+{
+    public static class StringUtils
+    {
+        public static string UpperCamelCaseToDashCase(this string str)
+        {
+            // If it's single letter variable, leave it as it is
+            if (str.Length == 1)
+            {
+                return str;
+            }
+
+            return string.Concat(str.Select((x, i) => i > 0 && char.IsUpper(x) ? "-" + x.ToString() : x.ToString())).ToLower();
+        }
+    }
+}