Add publication type to the returned metadata for PubMed records

[bill-baumgartner]

PubMed includes a publication type metadata attribute for each record. For example, see the PT lines of this record which indicates that this is a Journal Article and a Review.

Changes required:

• Backend schema needs to be updated to include this new piece of metadata
• Code that parses PubMed needs to be extended to extract the publication type for each record

Note: this was discussed during the DM call on 3/16/23
Note: we should check in with the UI team to confirm they are interested in this new metadata before proceeding