perf: shave off some bytes by using peek() more often

[bartveneman]

flowing out of testing #99

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.08%. Comparing base (346e143) to head (fef8b9b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #105      +/-   ##
==========================================
- Coverage   95.09%   95.08%   -0.01%     
==========================================
  Files          15       15              
  Lines        2568     2565       -3     
  Branches      665      662       -3     
==========================================
- Hits         2442     2439       -3     
  Misses        126      126              

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[codecov-commenter]

Bundle Report

Changes will decrease total bundle size by 222 bytes (-0.16%) ⬇️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
@projectwallace/css-parser-esm	138.49kB	-222 bytes (-0.16%) ⬇️

Affected Assets, Files, and Routes:

view changes for bundle: @projectwallace/css-parser-esm

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
tokenize.js	-222 bytes	15.08kB	-1.45%

Files in tokenize.js:

• ./src/tokenize.ts → Total Size: 14.52kB