Bug 36953: Add 678 to authority index (MARC21)

This enhancement adds field 678 to the default MARC21 authority index mappings.

To test:
1. Import the attached .mrc file
2. Go to Authorities
3. Search "Entire record" for innu
   --> No results
4. Go to the OPAC > Authority search
5. Search "in the complete record" for innu
   --> No results
6. Apply patch
7. Reindex authorities (in KTD shell:
   koha-elasticsearch --rebuild -a -v -r kohadev)
8. Redo step 3
   --> 1 result
9. Redo steps 4-5
   --> 1 result

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>

admin/searchengine/elasticsearch/mappings.yaml

@@ -1,5 +1,17 @@
 ---
 authorities:
+  Biographical-note:
+    label: Biographical-note
+    mandatory: ~
+    mappings:
+    - facet: ''
+      marc_field: 678(ab)
+      marc_type: marc21
+      sort: 1
+      suggestible: ''
+    opac: 1
+    staff_client: 1
+    type: ''
   Corporate-name-see-also-from:
     label: Corporate-name-see-also-from
     mandatory: ~