Unsquash images in docs

[drbenvincent]

• Closes Images in the docs are squashed  #425
• Constrains version to myst-nb<=1.0.0. Though this seems suboptimal because it's on version 1.2.0 now. I've tried building docs locally with the latest version but that still suffers from the same squashed image problem.

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📚 Documentation preview 📚: https://causalpy--439.org.readthedocs.build/en/439/

[drbenvincent]

Failing checks will hopefully be resolved in #437, but open to any input :)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.40%. Comparing base (0d6e4f8) to head (e92eea6).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #439   +/-   ##
=======================================
  Coverage   94.40%   94.40%           
=======================================
  Files          31       31           
  Lines        1985     1985           
=======================================
  Hits         1874     1874           
  Misses        111      111           

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[drbenvincent]

Seems to have fixed things in the docs