Optionally support long_description in CLI

[indigoviolet]

🚀 Feature request

Currently, CLI() uses short_description from the parsed docstring

I would like an option to include the long description in the help string.

Motivation

Sometimes there is useful content in the long description which is hidden from the user unless they read the script, or the writer explicitly breaks out that into a help string and sidesteps the docstring parsing functionality, making the docstring less useful for a developer.

Pitch

Add an option to CLI() like include_docstring_long_description.

Alternatives

Use a separate variable and pass it in as CLI(description=...)