Provide a default Docker registry or layer cache by default

[damienalexandre]

Right now this template provides a good GH Action boilerplate: https://github.com/jolicode/docker-starter/blob/main/.github/workflows/ci.yml

But it's building the whole project docker images every time.

The template should be optimized for future projects to have good test performances by default.

[lyrixx]

Would you mind to create a PR?

[matthieuwerner]

In progress 🤞