fix: refresh StreamingImageSequenceRenderer during OnEnable() (#457)

Author: sindharta

Runtime/Scripts/StreamingImageSequenceRenderer.cs

@@ -3,6 +3,10 @@
 using UnityEngine.Assertions;
 using UnityEngine.UI;
 
+#if UNITY_EDITOR
+using UnityEditor.Timeline;
+#endif
+
 namespace Unity.StreamingImageSequence  {
 
 /// <summary>
@@ -42,6 +46,10 @@ public sealed class StreamingImageSequenceRenderer : MonoBehaviour {
 
     void OnEnable() {
         InitImageComponent();
+        
+#if UNITY_EDITOR
+        TimelineEditor.Refresh(RefreshReason.SceneNeedsUpdate);
+#endif
     }
 
     internal void Init() {