Single- and double-dashed options with the same name should be allowed

[natecook1000]

Options with the same name, but different number of dashes, are currently prohibited by the name validator.

ArgumentParser version: 0.3.0
Swift version: Swift version 5.3 (swiftlang-1200.0.28.1 clang-1200.0.30.1)

Checklist

• If possible, I've reproduced the issue using the master branch of this package
• I've searched for existing GitHub issues

Steps to Reproduce

For example, changing the Repeat example's count property to this:

    @Option(name: [.long, .customLong("count", withSingleDash: true)],
            help: "The number of times to repeat 'phrase'.")
    var count: Int?

results in:

Fatal error: Validation failed for `Repeat`:

- Multiple (2) `Option` or `Flag` arguments are named "count".

Expected behavior

Either -count or --count should work for that option.

Actual behavior

The error shown above.