CLI-1406: Command documentation markup

[danepowell]

Motivation

Fixes CLI-1406

Proposed changes

Alternatives considered

Ideally we'd fix or extend the JsonDescriptor instead of handling this in post-processing. Unfortunately, all the JsonDescriptor methods are private and the Descriptor base class is marked as internal.

Testing steps

1. Follow the contribution guide to set up your development environment or download a pre-built acli.phar for this PR.
2. If running from source, clear the kernel cache to pick up new and changed commands: ./bin/acli ckc
3. Check for regressions: (add specific steps for this pr)
4. Check new functionality: (add specific steps for this pr)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.91%. Comparing base (449792d) to head (e66aa57).
Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1833      +/-   ##
============================================
+ Coverage     92.62%   92.91%   +0.28%     
  Complexity     1843     1843              
============================================
  Files           123      123              
  Lines          6959     6960       +1     
============================================
+ Hits           6446     6467      +21     
+ Misses          513      493      -20     

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[github-actions]

Try the dev build for this PR: https://acquia-cli.s3.amazonaws.com/build/pr/1833/acli.phar

curl -OL https://acquia-cli.s3.amazonaws.com/build/pr/1833/acli.phar
chmod +x acli.phar