add transition for toolbar appearing and disappearing

lib/widgets/editor/editor_toolbar.dart

@@ -60,6 +60,8 @@ class EditorToolbar extends HookWidget {
       create: (context) => store,
       child: AsyncStoreListener(
         asyncStore: store.imageUploadState,
+        child: AnimatedSwitcher(
+          duration: const Duration(milliseconds: 200),
           child: visible
               ? Container(
                   height: _height,
@@ -77,6 +79,7 @@ class EditorToolbar extends HookWidget {
                 )
               : const SizedBox.shrink(),
         ),
+      ),
     );
   }