Add conformances to support Swift ArgumentParser? #88

struct
Calculate : ParsableCommand
{
	@Option(name: .shortAndLong, help: "Path to input word list, one per line")
	var inputWordList: Path = Path.cwd/"wordlist.txt"
}

extension
Path : ExpressibleByArgument
{
	public init?(argument: String) {
		if let p = Path(argument)
		{
			self = p
		}
		else
		{
			return nil
		}
	}
}