🐛 #294 - fix: darkmode now works in the theme designer

[Xaohs]

closes #294
As discussed:

• For now hardcoded (just like Purple Rain theme) but hopefully we can refactor this to be more dynamic in the future (and be able to view all our themes in storybook dynamically)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.81%. Comparing base (7090bc4) to head (b9a373c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #295      +/-   ##
==========================================
- Coverage   91.86%   91.81%   -0.05%     
==========================================
  Files         200      200              
  Lines        8417     8417              
  Branches     1239     1237       -2     
==========================================
- Hits         7732     7728       -4     
- Misses        682      686       +4     
  Partials        3        3              

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