fix: calculate box width without escape sequence chars

[yongqi14]

resolves #316

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 29.31%. Comparing base (24c98ce) to head (2711393).
Report is 43 commits behind head on main.

Files with missing lines	Patch %	Lines
examples/box.ts	0.00%	4 Missing ⚠️
src/utils/box.ts	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #336       +/-   ##
===========================================
- Coverage   61.08%   29.31%   -31.77%     
===========================================
  Files          13       42       +29     
  Lines        1380     1644      +264     
  Branches       58       87       +29     
===========================================
- Hits          843      482      -361     
- Misses        537     1135      +598     
- Partials        0       27       +27     

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[pi0]

Thnx!