Add copier (or cookiecutter) template

[mfhepp]

Add / generate a Cookiecutter template to the project so that it can be used as a blueprint for new projects.

TBC: How can the cookiecutter package itself run only inside a Docker container for better isolation?

[mfhepp]

TBC: How can the cookiecutter package itself run only inside a Docker container for better isolation?

Reply to self: By creating a minimal environment and script based on the py4docker template.

[mfhepp]

It is more likely that this will be based on https://copier.readthedocs.io/en/stable/

[mfhepp]

Maybe turning it into a Github template would be sufficient as a minimal solution:

1. Change Github configuration. (done)
2. Update README and include example of using the Github CLI