Add CITATION.cff

[gonzalocasas]

Adds a CITATION.cff so that GitHub's Cite this repository button and Zenodo get proper citation metadata.

At the moment the repository has no citation file, so Zenodo builds each release's author list from GitHub contributors. The 2.15.1 record (10.5281/zenodo.19115881) lists GitHub handles ("beverlylytle", "deviezeviking"), surname-only entries ("Li", "Rippmann") and Romana Rust twice.

• Authors follow AUTHORS.md exactly, in its order: project lead, main developers, then contributors (38 people). Emails are left out.
• DOI is the concept DOI 10.5281/zenodo.2594510, which always resolves to the latest release.
• No version or date-released, so the file doesn't go stale between releases. Zenodo adds the version itself.
• Validated with cffconvert --validate (schema 1.2.0).

Once merged, the next release's Zenodo record should take its authors from this file. The "Cite COMPAS" block on the new compas.dev homepage will then use the same list.

What type of change is this?

• Bug fix in a backwards-compatible manner.
• New feature in a backwards-compatible manner.
• Breaking change: bug fix or new feature that involve incompatible API changes.
• Other (e.g. doc update, configuration, etc)

Checklist

• I added a line to the CHANGELOG.md file in the Unreleased section under the most fitting heading (e.g. Added, Changed, Removed).
• I ran all tests on my computer and it's all green (i.e. invoke test). (No code changes.)
• I ran lint on my computer and there are no errors (i.e. invoke lint). (No code changes.)

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.38%. Comparing base (d114251) to head (82a7140).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1533      +/-   ##
==========================================
- Coverage   62.40%   62.38%   -0.02%     
==========================================
  Files         208      208              
  Lines       22487    22487              
==========================================
- Hits        14032    14028       -4     
- Misses       8455     8459       +4     

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[chenkasirer]

LGTM!
Just linking a related work on CT where CITATION.cff is the single-source-of-truth and a bunch of other places reference it.

gramaziokohler/compas_timber#832

One thing we found out: PyPi will ignore the list of authors in pyproject.toml if they all have an email and will just show the top one.