Review CI setup

[tm-kn]

• Update the CI tooling to use the newest and shiniest stuff from https://github.com/wagtail/cookiecutter-wagtail-package.
• Use PyPI trusted publishing to the list.
• The nightly job does not seem to execute front-end tooling.
• I don't know how the publish job could've worked if the front-end tooling had missing src/ in the paths. See Fix inability to compile static files because of the missing src/ prefix in the paths #21.

Tasks

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1. Update the CI tooling to use the newest and shiniest stuff from https://github.com/wagtail/cookiecutter-wagtail-package.
2. Use PyPI trusted publishing (Switch to using PyPI trusted publishing #45)
3. Ensure front-end tooling is executed in the nightly job (Compile assets in nightly tests, and use Node 20 everywhere #50)

[zerolab]

Good call!
I would add "Use PyPI trusted publishing to the list" (https://docs.pypi.org/trusted-publishers/using-a-publisher/, https://github.com/wagtail/cookiecutter-wagtail-package/blob/main/%7B%7B%20cookiecutter.__project_name_kebab%20%7D%7D/.github/workflows/publish.yml#L31-L52)

[tomusher]

The addition of the src/ folder was recent - we haven't published a version since then. Thanks for picking up on that.

The CI setup is built on https://github.com/wagtail/cookiecutter-wagtail-package so we might be able to backport some of the recent fixes from there here, where it makes sense.

[zerolab]

This is now complete.