As mentioned in IS, I would suggest to skip the composer.json file entirely. ...

As mentioned in IS, I would suggest to skip the composer.json file entirely. It doesn't serve any purpose in this particular module. It's better to let drupal.org packaging create a valid composer.json. Of course, if it's likely this module will depend on PHP packages in the future, then it's useful to keep the composer.json, but I don't think that's the case.