Add CC-BY-4.0 license to the AI policy

[IAlibay]

I would like to propose that the AI policy is placed under CC-BY-4.0. It would be useful for downstream projects.

LLM/AI disclosure

No AI was used here.

PR Checklist

• Issue raised/referenced?
• Tests updated/added?
• Documentation updated/added?
• package/CHANGELOG file updated?
• Is your name in package/AUTHORS? (If it is not, add it!)
• LLM/AI disclosure was updated.

Developers Certificate of Origin

I certify that I can submit this code contribution as described in the Developer Certificate of Origin, under the MDAnalysis LICENSE.

---

📚 Documentation preview 📚: https://mdanalysis--5232.org.readthedocs.build/en/5232/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.81%. Comparing base (e6c1b44) to head (a7a5a5f).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #5232      +/-   ##
===========================================
- Coverage    93.83%   93.81%   -0.03%     
===========================================
  Files          180      180              
  Lines        22475    22475              
  Branches      3190     3190              
===========================================
- Hits         21090    21085       -5     
- Misses         923      926       +3     
- Partials       462      464       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[orbeckst]

great idea!

[IAlibay]

@RMeli @tylerjereddy @BradyAJohnston - I will need your approvals before I can merge this, since you have all contributed to the text.