Fix syntax highlighting on readthedocs

[cchwala]

• closes Syntax highlighting on readthedocs does not work #22
• Tests added and passed if fixing a bug or adding a new feature
• All code checks from pre-commit passed
• Added an entry in the CHANGELOG.md file

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (61c4063) 100.00% compared to head (4593188) 100.00%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #23   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines           43        43           
=========================================
  Hits            43        43           

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[cchwala]

Syntax highlighting works now, see https://poligrain--23.org.readthedocs.build/en/23/notebooks/Calculate_distances.html