add json array support to unity

JsonHelper.cs

 public class JsonHelper
 {
     public static T[] getJsonArray<T>(string json)
     {
         string newJson = "{ \"array\": " + json + "}";
         Wrapper<T> wrapper = UnityEngine.JsonUtility.FromJson<Wrapper<T>>(newJson);
         return wrapper.array;
     }
 
     [System.Serializable]
     private class Wrapper<T>
     {
         public T[] array;
     }
 }