Auotgenerate the --help output for the README

This is a nice write up of how to use cog to automatically add tool --help ouput to a README file and test that it is up to date as well.

https://til.simonwillison.net/python/cog-to-update-help-in-readme

Start by reading the linked Cog write-up and inspecting how circup currently documents its --help output in the README. Identify the command or documentation entry point involved; done means the README help text is generated automatically and a check can detect when it is out of date. No file or test path is named in the issue.

Written by the indexing model from the issue text.