feat(gha): improve ci

[aldbr]

• Add release-please in the loop: each push to main generates a PR which updates the changelog based on the latest commits (need to follow the conventional commit rules to work), and bumps the package version (prereleases). Once the PR is merged, a new tag/release is created, and a new image is pushed to the registry.
• Add commitlint to make sure the commits are following conventional commit rules.
• Edit the README.

Example of a generated tag: https://github.com/aldbr/diracx-web/releases/tag/v0.1.0-a1
Example of a generated release: https://github.com/aldbr/diracx-web/releases (a lot of useless info here but expected for the 1st release. Note that we could edit the changelog within the merged PRs but they would need to be squashed, see https://github.com/googleapis/release-please?tab=readme-ov-file#how-can-i-fix-release-notes)

And the generated images: https://github.com/aldbr/diracx-web/pkgs/container/diracx-web%2Fstatic

Why release-please?

1. it could work with both python and node projects
2. it provides a good balance of automation and ease of use
3. it can handle multi-package repositories

[fstagni]

I will look into the details later on, but these are things that, if applied, should not be done for only diracx-web. I am not saying to apply to DIRAC, but at least to diracx.