feat: allow passing of exit code to outputHelp and outputVersion

[spiltcoffee]

Fixes #45

[codecov-io]

Codecov Report

Merging #46 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master      #46   +/-   ##
=======================================
  Coverage   57.55%   57.55%           
=======================================
  Files           5        5           
  Lines         344      344           
  Branches       77       87   +10     
=======================================
  Hits          198      198           
  Misses        144      144           
  Partials        2        2

Impacted Files	Coverage Δ
src/CAC.ts	68.75% <0%> (ø)	⬆️
src/Command.ts	26.19% <0%> (ø)	⬆️

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