Bug 28235: Correct CSS governing max width of custom cover images

Bug 28235: Correct CSS governing max width of custom cover images

Images shown in the OPAC and staff interface when the
OPACCustomCoverImages and  CustomCoverImages preferences are enabled
should be getting a max-width set in the current CSS, but the order of
the declarations is preventing the correct specificity.

This patch moves the CSS to the correct place in each file so that the
max-width is applied.

To test, apply the patch and rebuild both the staff and OPAC CSS. If you
get an error during the build process you may need to run 'yarn
install.'

- Go to Administration -> System preferences, and enable the
  OPACCustomCoverImages and  CustomCoverImages preferences.
- If you're testing with the default test database you can set the
  CustomCoverImagesURL preference to
  https://static.myacpl.org/public/covers/{normalized_isbn}.jpg
- Perform a catalog search in both OPAC and staff client limiting by
  itemtype = 'Book'.
- The search results in both interface should show several covers
  supplied from the external URL.
- In the staff client, these images should be limited to 140px wide even
  if the source image is larger.
- In the OPAC, view the detail page for one of the results with cover
  images. The image shown on the detail page should be constrained to
  140px wide even if the source image is larger.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>