Bug 39444: Make Standard consider pubmedid field

This field may be added by a plugin or jQuery, so Standard should consider it as a possibility.
This patch does not change anything for existing users that do not add a 'pubmed id' field themselves.

1) Enable ILLModule
2) Install the ILL Actions plugin:
https://github.com/PTFS-Europe/koha-plugin-ill-actions/releases/tag/v2.0.1
3) Create a new ILL request:
http://localhost:8081/cgi-bin/koha/ill/ill-requests.pl?method=create&backend=Standard
4) Pick type: 'Journal article', notice a top pop-up for DOI/PubMed ID now shows. This is coming from the plugin.
5) Add something to the pubmedid input like '123'. Notice the metadata is auto-filled.
6) Add a patron cardnumber '42'. Notice the library is automatically picked. Click 'Create'.
7) On the manage request screen, notice the PubMed ID is not shown. This is because it was not saved.
8) Apply patch and repeat.

Signed-off-by: Jeremy Evans <jeremy.evans@ukhsa.gov.uk>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Edit (tcohen): adapted to 38339
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>

Koha/ILL/Backend/Standard.pm

@@ -957,6 +957,8 @@ sub _get_core_fields {
         published_date  => __('Publication date'),
         published_place => __('Place of publication'),
         publisher       => __('Publisher'),
+        pubmedid        => __('PubMed ID'),
+        pmid            => __('PubMed ID'),
         sponsor         => __('Sponsor'),
         studio          => __('Studio'),
         title           => __('Title'),