This PR solves issue #819 by programmatically adding categories enumerated here. Multiple categories are delimited by semicolons without spaces, and inserted immediately after the ID within the div tag.
with @tcatapano, we think this is simply because category attribute has not been added to the schema (see https://github.com/cu-mkp/m-k-manuscript-data/blob/afaa7453e41f050fea8fa2dadf58220e9cae5857/schema/ms-transcription.rng#L65-L75)
Will determine full scope and merge the pull request tomorrow