content/static/css: update style of feedback button to behave like a link
content/static/css: update style of feedback button to behave like a link

Some browsers have background and padding set in their user-agent
stylesheets. Ensure it looks and behaves like the other elements in
the footer (along with underline on hover).

Also fixes some formatting bugs via prettier auto-format.

Fixes b/143641315

Change-Id: I4747ab7867d1ff10be327258ea7cd29eeaabbdcf
Reviewed-on: https://team-review.git.corp.google.com/c/golang/discovery/+/588353
CI-Result: Cloud Build <ea5729d4cf3392b9d382b6ca272c65aa27554f44@system.gserviceaccount.com>
Reviewed-by: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite