[Feature Request] Invocation examples

Please add examples to the help text, per command.

As done for [Spectre.Console](https://spectreconsole.net/cli/commands#configuring). (Examples are optional; they are specified in code, they aren't created dynamically.)

e.g. `myapp foo --help` will also print this:
````
EXAMPLES:
myapp foo
myapp foo -f somefile.txt
myapp foo --file somefile.txt
````