fix: add style while generating local fallbacks for variable

[qwerzl]

I noticed this problem while testing. While adding local fallbacks for variable fonts, styles should also be added.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (main@0913b4b). Click here to learn what that means.

Files	Patch %	Lines
src/css/parse.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #110   +/-   ##
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  Coverage        ?   64.60%           
=======================================
  Files           ?       41           
  Lines           ?     2639           
  Branches        ?      425           
=======================================
  Hits            ?     1705           
  Misses          ?      909           
  Partials        ?       25           

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