Set custom-style to "Bibliography" on reference sections

The "Bibliography" style is applied by pandoc for reference sections,
but here this has to be done by the filter, since pandoc doesn't
recognize the topic bibliographies as reference sections.

Closes: pandoc-ext#14

Author: tarleb

_extensions/multibib/multibib.lua

@@ -135,6 +135,13 @@ local function create_topic_bibliography (div)
   -- Set the classes and attributes as citeproc did it on refs_div
   div.classes = remove_duplicates(refs_div_with_properties.classes)
   div.attributes = refs_div_with_properties.attributes
+  if FORMAT == 'odt' or FORMAT == 'docx' then
+    -- Pandoc assignes the "Bibliography" to reference sections in Word, so
+    -- let's do it here, too, unless it's already set.
+    div.attributes['custom-style'] = div.attributes['custom-style']
+      or 'Bibliography'
+  end
+
   return div
 end