fix: use onError callback of super_clipboard to work with async await using dart Completer

flutter_quill_extensions/lib/services/clipboard/super_clipboard_service.dart

@@ -41,10 +41,14 @@ class SuperClipboardService implements ClipboardService {
     final reader = await clipboard.read();
     final completer = Completer<Uint8List>();
 
-    reader.getFile(format, (file) async {
+    reader.getFile(
+      format,
+      (file) async {
         final bytes = await file.readAll();
         completer.complete(bytes);
-    });
+      },
+      onError: completer.completeError,
+    );
     final bytes = await completer.future;
     return bytes;
   }