docs: Add Dart Package peanut for Flutter

Author: peaceiris

README.md

@@ -809,9 +809,12 @@ jobs:
 An exapmle workflow for [Flutter web project].
 Setup [Flutter] with [subosito/flutter-action].
 
+[peanut | Dart Package] is also useful.
+
 [Flutter]: https://github.com/flutter/flutter
 [Flutter web project]: https://flutter.dev/docs/get-started/web
 [subosito/flutter-action]: https://github.com/subosito/flutter-action
+[peanut | Dart Package]: https://pub.dev/packages/peanut
 
 ```yaml
 name: github pages