Add CITATION.cff and Zenodo metadata file

[Neves-P]

This PR adds a .zenodo.json with metadata that should be automatically read upon release of a new version. It will result in automatically archiving this repository with the correct metadata.

Additionally, it contains a CITATION.cff file with more minimal information, but that is automatically recognized by GitHub.

Please confirm the author personal information and affiliations are correct.

Warning

The GitHub/Zenodo integration needs to be enabled before marking the release on GitHub, otherwise it will not work. The steps described here must first be followed by the person making the release for this repository and the GitHub integration for this repository must be enabled on the Zenodo interface.

Here is a step-by-step guide:

1. Review PR and confirm info about authors is correct
2. Log in to Zenodo and link it to your GitHub account if you haven't already; it must be the same account that you use to tag the release. You can do so here: https://zenodo.org/account/settings/linkedaccounts/
3. Go to https://zenodo.org/account/settings/github/ and flip the main switch at the top to ON and then the switch for the isc26-tutorial repository. If you don't see the repository, go back to the GitHub account linking and make sure you also give it permissions to the EESSI organisation
4. Go back to https://eessi/isc26-tutorial and tag a new release as v1.0. The release notes will be added to the Zenodo metadata but that can be changed later in case something is wrong
5. A Zenodo entry should automatically be created and appear on your dasboard: https://zenodo.org/me/uploads?q=&f=shared_with_me%3Afalse&l=list&p=1&s=10&sort=newest

No major problem if it doesn't work since we can always manually do it. But this is a nice "dress rehearsal" for new documentation and event PRs

[Neves-P]

Note: event is not a supported type in CFF files. Software was the one that matched the closest, imho.