Add sections to allow some customisation of help layout

[shadowspawn]

Pull Request

I wanted to give this a try, but not sure it adds enough value or is easy enough to use. Opening a draft with proof of concept.

Problem

It isn't convenient to customise the order of sections in the Help.

See #1870

Solution

Create "sections" in formatHelp and call visibleSections which can be overridden to customise the list. Some possible use cases:

• reorder sections
• hide sections
• alter section titles, like make bold or all capitals
• add own (pre-formatted) sections, like "Environment Variables" or "Examples"
• (maybe) replace single-line Usage with multi-line usages

Example client code to put options after commands:

program.configureHelp({
  visibleSections: (sections) => {
    // Hide empty sections.
    const visible = sections.filter((section) => !!section.body);
    // Reorder sections.
    const order = ['usage', 'description', 'arguments', 'commands', 'options', 'globalOptions'];
    return visible.sort((a, b) => {
      return order.indexOf(a.name) - order.indexOf(b.name);
    });
  }
});

ChangeLog