Add nested commands

[cristaloleg]

Fixes #1

[codecov-commenter]

Codecov Report

Merging #2 (91e990f) into main (ba9e95d) will decrease coverage by 1.44%.
The diff coverage is 90.47%.

@@             Coverage Diff             @@
##              main       #2      +/-   ##
===========================================
- Coverage   100.00%   98.55%   -1.45%     
===========================================
  Files            2        2              
  Lines          124      138      +14     
===========================================
+ Hits           124      136      +12     
- Misses           0        1       +1     
- Partials         0        1       +1     

Impacted Files	Coverage Δ
acmd.go	98.23% <90.47%> (-1.77%)	⬇️

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[cristaloleg]

ping @crayoned @quasilyte