Bug 30077: (follow-up) Set max width for library drapdown

Bug 30077: (follow-up) Set max width for library drapdown

If you have a library with a very long name the dropdown will expand to
accommodate it. I think this is awkward-looking, so I propose to set a
max width on <select> elements in the header search region.

The patch requires a rebuild of the staff interface CSS:
https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client

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>