Which documentation?

CONTRIBUTING.md

What needs to be documented?

While https://github.com/scikit-hep/awkward/blob/2ca5ccd578d901e7dcfea1cde13c2ac79b13f872/CONTRIBUTING.md isn't necessarily out of date for development, there's sections like

that are. To help new contributors get going can this get a look to see if parts of the development workflow should be updated?