[Feature Request] Help section for details / notes / etc.

This is the current output for `app command --help`:
````
Description:
xxx

Usage:
xxx

Arguments:
xxx

Options:
xxx
````

Please consider adding more sections. Think of the average man page - it contains lots of detail; same for a typical `foo --help` command. They are often termed "description", "detail", "synopsis", etc.

It would be helpful to have such a section for a paragraph of explanatory text:
````
Description:
xxx

Details:
xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx
xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx
xxx xxx xxx xxx xxx

Usage:
xxx

Arguments:
xxx

Options:
xxx
````

I know it's possible achieve this through [customisation](https://docs.microsoft.com/en-us/dotnet/standard/commandline/customize-help), and that's the workaround that I'm using. But for something so common, it would be friendlier to have an extra help section.

If such a thing is added, please also allow it for the root help too, i.e. `app --help`.