feat: add class name to utrecht-theme for responsive scales

[Robbert]

Depends on #2242

De XS en 2XS van de font size scale werden eigenlijk niet gebruikt, omdat ze gewoon te klein zijn. Daarom haal ik ze weg. De enige toepassing van XS (blockquote caption) heb ik aangepast naar SM.

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Name	Status	Preview	Comments	Updated (UTC)
utrecht	❌ Failed (Inspect)			Oct 13, 2024 4:18pm

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 93.88%. Comparing base (e4515df) to head (aae51d0). Report is 43 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2567   +/-   ##
=======================================
  Coverage   93.88%   93.88%           
=======================================
  Files         154      154           
  Lines        1308     1308           
  Branches      284      285    +1     
=======================================
  Hits         1228     1228           
  Misses         79       79           
  Partials        1        1           

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