feat(cli): add help command

[galvez]

Following convention used in vue and other tools like kubectl (Kubernetes).

nuxt help <command>

@pi0 still need to add tests, but welcome early feedback as usual :)

[codecov-io]

Codecov Report

Merging #4248 into dev will decrease coverage by 0.58%.
The diff coverage is 38.09%.

@@            Coverage Diff             @@
##              dev    #4248      +/-   ##
==========================================
- Coverage   92.98%   92.39%   -0.59%     
==========================================
  Files          51       52       +1     
  Lines        1696     1710      +14     
  Branches      438      442       +4     
==========================================
+ Hits         1577     1580       +3     
- Misses        116      124       +8     
- Partials        3        6       +3

Impacted Files	Coverage Δ
packages/cli/src/commands/help.js	0% <0%> (ø)
packages/cli/src/commands/index.js	100% <100%> (ø)	⬆️
packages/cli/src/run.js	35.48% <60%> (-3.92%)	⬇️
packages/cli/src/command.js	90.27% <80%> (-0.77%)	⬇️

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[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.