Tweak the Pluto to Documenter pipeline

[maltezfaria]

• Fix broken links (Crossrefs broken in Pluto notebooks #95)
• Cache setup stages of doc build
• Error if broken links are present in docs

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.93%. Comparing base (597cc23) to head (523b466).
Report is 12 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #102       +/-   ##
===========================================
- Coverage   79.97%   65.93%   -14.04%     
===========================================
  Files          24       24               
  Lines        3021     3018        -3     
===========================================
- Hits         2416     1990      -426     
- Misses        605     1028      +423     

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[maltezfaria]

@gregoirepourtier I made a few minor changes to your original implementation. My goal was to keep it simple for now. We can always make a more complex workflow later if we feel it is needed.

[gregoirepourtier]

Apart from the description of the generated example, everything else LGTM :)