Auto generate documentation for python scripts in README.md file

Here is a simple way to keep README document in-sync if you have a number of things to document.

And it looks like this:

Each script needs to response to --help when called which is then collected and rendered into README.md between a set of pre-configured tokens.

readme_docs.py contains the code to generate this documentation.

It is also configured as a pre-commit hook so that we always keep it up to date.

      - id: readme-docs
        name: Readme documentation
        description: Using [python help], inserts into README.md.
        entry: python3 readme_docs.py
        language: system
        pass_filenames: false