Choices for arguments

[shadowspawn]

Pull Request

Problem

We have .choices() for options but not for arguments.

Issue: #1458
Past issue: #971

Solution

Follow same pattern as Option with the new Argument class, and add .choices().

program
  .addArgument(new Argument('color').choices(['red', 'blue']))

$ node example.js purple
error: command-argument value 'purple' is invalid for argument 'color'. Allowed choices are red, blue.

Includes some tests and typings for .default() and .argParser() that got missed.

ChangeLog

• .addArgument() (More consistent way of adding command arguments #1490)
  • Argument supports .choices() (Choices for arguments #1525)

[shadowspawn]

Rebased onto release/8.x.

[abetomo]

LGTM!