Work out how to auto-update the example

[coretl]

A possibility is to let dependabot report when things change, including release notes, then run CI that updates the dependabot PR with the code from copier update.

Details:

• Publish python-copier-template to PyPI
• Add it as a dev dependency
• Add it to dependabot as a separate group, with particular title
• Add a new workflow that triggers on PRs with that title that does copier update --vcs-ref $(python -m python-copier-template --version) and adds the result to the PR

Issues:

• This will fail if you do a local update, not sure how to solve this...

[coretl]

Maybe we should be less clever, and just do this via a periodic job, like https://github.com/scientific-python/cookie/blob/main/.github/workflows/bump.yml

[coretl]

Or push via an SSH deploy key using SSH agent

[coretl]

Fixed in #65