Source information missing from parsed nodes

I'm making a renderer that will modify a tree in-place, but can roundtrip MarkDown back to the same MarkDown (or mostly the same).

There is some information missing from the parsed nodes that would be useful reconstructing the original document. In particular:

• Whether a code_block was originally fenced or indented.
• What symbol was used for emphasis, either * or _.

Can these be added to the parse nodes?

Begin by locating the parser code that creates parsed nodes and the handling for code_block and emphasis. Check how node attributes are represented and how existing parser tests cover these constructs. Done means nodes preserve fenced-versus-indented origin and the * versus _ emphasis marker, with tests demonstrating both cases.