Document a method for including transfer docs in an interview repo #472

For more complex interviews, it can be useful to start with a flowchart that can be approved by stakeholders. Then the interview can be tested against the flowchart.

Perhaps more critically, some jurisdictions have complex e-filing logic. Documenting this logic as a Mermaid flowchart in the repo would make it possible for the court or org to request changes like any other pull request, and give the developer(s) clear guidance for implementing those changes in the code.

I think we should probably add a docs folder in interview repos when they contain flowcharts or other documentation (such as transfer memos).