Bug 32261: Add more UI feedback when selecting patron from autocomplete

Bug 32261: Add more UI feedback when selecting patron from autocomplete

There is only a tiny change in the color of the selected item, but it's
not obvious.

Test plan:
Regenerate the css files using `yarn build`
Search for patrons and note that the down/up keys let you select a
patron and the background color change.
Note that the background color is not on the container and so is not
similar as the hover rule (when using the mouse). We could change that,
but then the behaviour is weird when you have both the mouse and the
keyboard selecting items in the item list.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jacob O'Mara <jacob.omara@ptfs-europe.com>