Small ResourceManager refactor, add ResourceSaver<T>.

DaggerFramework/Source/SceneGraph/Resources/SerializedScene.cs

@@ -0,0 +1,20 @@
+using System.Text.Json.Serialization;
+
+namespace DaggerFramework.SceneGraph
+{
+    public class SerializedScene : Resource
+    {
+        public Dictionary<string, Layer> Layers { get; set; }
+
+        public SerializedScene(string path, byte[] buffer) : base(path, buffer)
+        {
+        }
+    }
+
+    [JsonSourceGenerationOptions(WriteIndented = true)]
+    [JsonSerializable(typeof(SerializedScene))]
+    internal partial class SerializedSceneContext : JsonSerializerContext
+    {
+
+    }
+}