Allow app author to answer rating comments

**Note: This proposed enhancement has been edited because the spam reporting feature has been already implemented.**

Please consider allowing app authors to answer rating comments, like on WordPress's rating pages.

The rating system allows anybody with an account on 'apps.nextcloud.com' to leave a rating for any app and this is fair enough, but the app's author has to be allowed to answer rating comments, since they can be posted by people with bad intentions or by people who never used the app.

Publishing good, gratis free and open source apps in the Nextcloud app store can lower the potential income for some companies that develop similar paid proprietary apps, so, there are reasons for some anonymous users to leave bad ratings to certain apps, in an effort to lower their popularity and stop their adoption. Also, there may be app authors who leave unjustified bad ratings to other apps just to see their own app moving higher in the list of 'best rated' apps.