🐛 change the document code of the issue sheet

[jgunstone]

If a project has custom document codes, then the code they require for the issue sheet might be different.
Currently the document code is hardcoded in:

document-issue/packages/document-issue-io/src/document_issue_io/issuesheet.py

Lines 304 to 312 in 677d7d3

	name = dict(
	project=projectinfo.get("Project Code"),
	originator="MXF", # TODO: remove hardcoding
	volume="XX",
	level="XX",
	infotype="IS",
	role="J",
	number="",
	)

The descriptions can be hardcoded but the codes should come from the lookup tables like everything else.