Bug 31294: Show "Required" label on mandatory fields

Bug 31294: Show "Required" label on mandatory fields

This patch adds "Required" label on mandatory fields for Article Requests

0. Apply the patch
1. koha-plack --restart kohadev
2. Change syspref 'ArticleRequests' to 'Enable'
3. Change syspref 'ArticleRequestsMandatoryFields' to '[Select all]'
4. Go to http://localhost:8080/cgi-bin/koha/opac-search.pl?idx=&q=test&weight_search=1
5. Click "Request article" for "Gairm"
6. Note that "Title", "Author", "Volume", "Issue", "Date", "Pages", and
   "Chapters" all say required
7. Change syspref 'ArticleRequestsMandatoryFields' to 'Title' and
   'Author'
8. Go to http://localhost:8080/cgi-bin/koha/opac-request-article.pl?biblionumber=29
9. Note that only "Title" and "Author" say required

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>