Validate that markup fields in json / yaml meet commonmark / similar formatting.

[butler54]

Issue description / feature objectives

OSCAL describe a subset of markdown that is supported for the markup data types. https://pages.nist.gov/OSCAL/reference/datatypes/#markup-data-types

Unfortunately this is not captured by our current schema.

Two options exist:

1. Create a validator / corrector that exists in the form of a trestle validation task
2. Formalize the spec as a class and make the validation part of the underlying pydantic infrastructure.

Either way a method will be needed to identify the matching elements which may devolve to a manual lookup table.