Autogenerate function .md or docs from definition

[andrewdavidmackenzie]

We can generate a .md file (used in book and in code comments via include or via flowmarco) from the parsed definition file. We know the path so can explain how to "use" it. We know the list of inputs and types We know the list of outputs and types We could add a Docs field to the definition that is the markdown text describing it.