Please document how to add help text after the auto-generated command list help

[sirlark]

The documentation covers in decent detail how to add help strings to each your groups, commands, and arguments but does not cover how to add general text to groups or the utility as a whole. I found the epilog field on the Group class but as far as I can tell it's entirely undocumented. Also, the indentation semantics are non-obvious. Finally, I can't find an equivalent for the script/app as a whole.

As an example of this feature, I wanted to add a usage example list after the auto-generated command/argument help text, such as in

Usage: clickdoc [OPTIONS] COMMAND [ARGS]...

  SQLFluff is a modular SQL linter for humans.

Options:
  --version   Show the version and exit.
  -h, --help  Show this message and exit.

Commands:
  docs  Generate some docs
  version   Show the version of clickdoc.

Examples:
  clickdoc docs a_path
  clickdoc docs --put-option-here