[euronion]

This PR adds a checklist for data PRs to the repository.
I tried to have it detailed and tried to remember the mental checklist I usually go through with PRs.

Second, this adds a Claude skill to support reviews. Not sure how well that will work - let's see.

@fneum or @danielelerede-oet could you review and comment?

Checklist

• Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
• Data source for new technologies is clearly stated.
• Newly introduced dependencies are added to environment.yaml (if applicable).
• A note for the release notes doc/release_notes.rst of the upcoming release is included.
• I consent to the release of this PR's code under the GPLv3 license.