Add chapter 10 sample project

Chapter10/TemplateStudioSampleApp.Core/Helpers/Json.cs

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+using Newtonsoft.Json;
+
+namespace TemplateStudioSampleApp.Core.Helpers;
+
+public static class Json
+{
+    public static async Task<T> ToObjectAsync<T>(string value)
+    {
+        return await Task.Run<T>(() =>
+        {
+            return JsonConvert.DeserializeObject<T>(value);
+        });
+    }
+
+    public static async Task<string> StringifyAsync(object value)
+    {
+        return await Task.Run<string>(() =>
+        {
+            return JsonConvert.SerializeObject(value);
+        });
+    }
+}