fix: allow number arg to be optional

[kricsleo]

resolves #193

[codecov]

Codecov Report

Attention: Patch coverage is 11.11111% with 8 lines in your changes missing coverage. Please review.

Please upload report for BASE (main@241b948). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/args.ts	11.11%	8 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #194   +/-   ##
=======================================
  Coverage        ?   93.92%           
=======================================
  Files           ?        7           
  Lines           ?      510           
  Branches        ?      164           
=======================================
  Hits            ?      479           
  Misses          ?       31           
  Partials        ?        0           

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[pi0]

thnx!