feat: fix nested css by swapping css-tree for @eslint/css-tree

[bartveneman]

Types currently incorrect: eslint/csstree#94

[codecov]

Bundle Report

Changes will increase total bundle size by 27 bytes (0.15%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
formatCss-esm	6.96kB	27 bytes (0.39%) ⬆️

Affected Assets, Files, and Routes:

view changes for bundle: formatCss-esm

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
format-*.js	27 bytes	6.96kB	0.39%

Files in format-*.js:

• ./index.ts → Total Size: 13.32kB

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (f0fd4c5) to head (5e4d5b2).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #132   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          307       308    +1     
  Branches        97        98    +1     
=========================================
+ Hits           307       308    +1     

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