Add JsonAsset::GetInstance<T> for easier access to C++ json asset data

Source/Engine/Content/JsonAsset.h

@@ -93,6 +93,16 @@ public:
     /// </summary>
     void* Instance;
 
+    /// <summary>
+    /// Gets the deserialized native object instance of the given type. Returns null if asset is not loaded or loaded object has different type.
+    /// </summary>
+    /// <returns>The asset instance object or null.</returns>
+    template<typename T>
+    T* GetInstance() const
+    {
+        return Instance && InstanceType.IsAssignableFrom(T::TypeInitializer) ? (T*)Instance : nullptr;
+    }
+
 protected:
 
     // [JsonAssetBase]