Support command examples

[akuntsch]

Is your feature request related to a problem? Please describe.
The problem of not being able to provide full command examples with descriptions.

Describe the solution you'd like
Support command examples with descriptions and show them in the auto-generated help text.

I'm thinking of something like this:

buildCommand({
  ...
  docs: {
    examples: [
      { command: 'mycommand --flag1 value1 ....', description: 'Does this and that' },
      ...
    ],
    ...
  },
  ...
});

Might also use an array of arrays like some other frameworks do, but I personally prefer explicit properties.

The generated help text should then have an EXAMPLES section where the examples are shown.

Describe alternatives you've considered
I tried using customUsage but there's not really a way to get the desired result with that.

Additional context
This feature is supported by many other cli frameworks and can be pretty useful imo.

[molisani]

This is a good idea, but I wonder if there would be some way to enhance the usage section to have documented use cases. I think having USAGE and EXAMPLES is a bit too repetitive and the existing USAGE section could use some more customizability.