New formats:
- `jats_archiving` for the "Archiving and Interchange Tag Set",
- `jats_publishing` for the "Journal Publishing Tag Set", and
- `jats_articleauthoring` for the "Article Authoring Tag Set."
The "jats" output format is now an alias for "jats_archiving".
Closes: #6014
The current DTD for the JATS writer template is for Journal Publishing (JATS-journalpublishing1.dtd), which does not permit ext-link as a valid child (https://jats.nlm.nih.gov/publishing/tag-library/1.1/element/publisher-name.html).
This update modifies the default output template to be the less restrictive JATS archiving and interchange DTD which systems like PubMed use internally to represent their articles.
Modified template to include a `<back>` and `<body>` section.
This should give authors more flexibility, e.g. to put
acknowledgements metadata in `<back>`. References are
automatically extracted and put into `<back>`.
