Re-add WebP artefacts

[tpvasconcelos]

Oops I forgot that the WebP images are also used by the main README file and not just the Sphinx docs...

---

📚 Documentation preview 📚: https://ridgeplot--304.org.readthedocs.build/en/304/

Copilot reviewed 8 out of 10 changed files in this pull request and generated no comments.

Files not reviewed (2)

• MANIFEST.in: Language not supported
• Makefile: Language not supported

Comments suppressed due to low confidence (1)

docs/conf.py:401

• The word 'artefacts' should be spelled 'artifacts' to be consistent with the rest of the code.

print(f"Writing image artefacts to {path_charts}...")

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (fdf0c6d) to head (7bfa94b).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #304   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           18        18           
  Lines          649       649           
  Branches        78        78           
=========================================
  Hits           649       649           

Flag	Coverage Δ
combined-src	99.84% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

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