Bug 21304: (follow-up) Fix style of search results browser

Bug 21304: (follow-up) Fix style of search results browser

This follow-up revises the style of the search result browser in the
staff client, making it behave better at smaller browser widths.

The patch also makes a couple of ESLint-prompted changes to browser.js

To test, apply the patch and regenerate CSS.

 - Perform a catalog search in the staff client.
 - Click on one of the search results.
 - On the bibliographic detail page there should be results browsing
   controls in the left-hand sidebar.
   - Resize the browser window and confirm that the controls work well
     at various sizes.
   - Test with both the first and last search result.

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>