Fix CSS @media query parsing error in style elements

[rursache]

Summary

• Skip unknown CSS @ rules (e.g. @media, @supports) including nested blocks when parsing style sheets
• Previously the parser would fail when encountering @media queries, printing a parsing error to console
• The scanner now tracks brace depth to correctly skip over nested rule blocks while continuing to parse surrounding selectors

Test plan

• Added skipsMediaQueries() test verifying @media blocks are skipped and surrounding selectors are parsed
• Added skipsNestedAtRules() test verifying doubly-nested @ rules (e.g. @supports containing @media) are skipped
• All 195 tests pass

Closes #59

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.43%. Comparing base (6238058) to head (ed1d5a7).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #119      +/-   ##
==========================================
+ Coverage   89.02%   89.43%   +0.41%     
==========================================
  Files         159      159              
  Lines       11959    15445    +3486     
==========================================
+ Hits        10646    13814    +3168     
- Misses       1313     1631     +318     

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[swhitty]

thank you