JATS writer: encode author "others" as <etal/>

Citeproc adopted the BibTeX convention to use the author name "others"
when there are additional authors that are not named. JATS uses the
`<etal>` element for this.

src/Text/Pandoc/Writers/JATS/References.hs

@@ -144,7 +144,9 @@ toNameElements :: Name -> Doc Text
 toNameElements name =
   if not (isEmpty nameTags)
   then inTags' "name" [] nameTags
-  else nameLiteral name `inNameTag` "string-name"
+  else if nameLiteral name == Just "others"  -- indicates an "et al."
+       then "<etal/>"
+       else nameLiteral name `inNameTag` "string-name"
     where
       inNameTag mVal tag = case mVal of
         Nothing  -> empty

test/command/7042.md

@@ -15,10 +15,11 @@ references:
   author:
   - family: Negidius
     given: Numerius
+  - literal: others
   container-title: Public Library of Tests
   id: access-date
   issued: 1911-10-03
-  title: Entry with access date
+  title: Entry with access date and et al.
   type: article-journal
 - author:
   - family: Beethoven
@@ -93,8 +94,9 @@ references:
       <element-citation publication-type="article-journal">
         <person-group person-group-type="author">
           <name><surname>Negidius</surname><given-names>Numerius</given-names></name>
+          <etal/>
         </person-group>
-        <article-title>Entry with access date</article-title>
+        <article-title>Entry with access date and et al.</article-title>
         <source>Public Library of Tests</source>
         <year iso-8601-date="1911-10-03">1911</year><month>10</month><day>03</day>
         <date-in-citation content-type="access-date"><year iso-8601-date="1999-01-22">1999</year><month>01</month><day>22</day></date-in-citation>