Make feedback button less obstrusive

Mathias Brodala reported an issue

The feedback button and especially the feedback bar at the bottom take a considerable amount of space from the extension repository view. Please consider making the button less obstrusive.

Reported URL:https://extensions.typo3.org/

User Agent:Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.119 Safari/537.36