chore: Disable image transition for better performance

lib/widgets/mxc_image.dart

@@ -157,13 +157,8 @@ class _MxcImageState extends State<MxcImage> {
   Widget build(BuildContext context) {
     final data = _imageData;
 
-    return AnimatedCrossFade(
-      duration: widget.animationDuration,
-      crossFadeState:
-          data == null ? CrossFadeState.showFirst : CrossFadeState.showSecond,
-      firstChild: placeholder(context),
-      secondChild: data == null || data.isEmpty
-          ? const SizedBox.shrink()
+    return data == null || data.isEmpty
+        ? placeholder(context)
         : Image.memory(
             data,
             width: widget.width,
@@ -176,7 +171,6 @@ class _MxcImageState extends State<MxcImage> {
               WidgetsBinding.instance.addPostFrameCallback(_tryLoad);
               return placeholder(context);
             },
-            ),
           );
   }
 }