add pack extension --help

[itsdarshankumar]

Summary

Added command to show output for "pack extension --help"

Output

Before

No such command exists before

Related

Resolves #1470

[codecov]

Codecov Report

Merging #1603 (f6d7a9c) into main (05c18f3) will decrease coverage by 1.05%.
The diff coverage is 69.39%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1603      +/-   ##
==========================================
- Coverage   80.62%   79.56%   -1.05%     
==========================================
  Files         156      163       +7     
  Lines       10563    10661      +98     
==========================================
- Hits         8515     8481      -34     
- Misses       1542     1668     +126     
- Partials      506      512       +6     

Flag	Coverage Δ
os_linux	79.34% <69.39%> (-0.09%)	⬇️
os_macos	77.39% <69.39%> (-0.10%)	⬇️
os_windows	79.47% <69.39%> (-1.05%)	⬇️
unit	79.56% <69.39%> (-1.05%)	⬇️

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[natalieparellano]

Apologies @itsdarshankumar, I may be confused - is this PR intended to resolve #1606, or just the --help aspect of pack extension? I think either approach is fine but just want to make sure we've linked to the right issue :)

[itsdarshankumar]

Apologies @itsdarshankumar, I may be confused - is this PR intended to resolve #1606, or just the --help aspect of pack extension? I think either approach is fine but just want to make sure we've linked to the right issue :)

@natalieparellano This PR is for --help, I'll add another PR for #1606

[jjbustamante]

I think this PR is ok to be merged, Darshan is also working in the implementation of each of the commands for extension on pack, and this one is required.

CC @samj1912 , @hone , @dfreilich , @jkutner

[natalieparellano]

@buildpacks/toc any thoughts on this one?