Scala Duration support

[joan38]

Hi,

Would you be open for me to open a PR to support scala.concurrent.duration.{Duration, FiniteDuration}?
As in:

  implicit val durationParser: ArgParser[Duration] =
    SimpleArgParser.from[Duration]("Duration")(s =>
      Either.catchOnly[NumberFormatException](Duration(s)).leftMap(e => MalformedValue("Duration", e.getMessage))
    )

  implicit val finiteDurationParser: ArgParser[FiniteDuration] =
    SimpleArgParser.from[FiniteDuration]("FiniteDuration")(s =>
      Either
        .catchOnly[NumberFormatException](Duration(s))
        .leftMap(e => MalformedValue("FiniteDuration", e.getMessage))
        .flatMap {
          case finite: FiniteDuration => Right(finite)
          case _ => Left(MalformedValue("FiniteDuration", s"Expected finite duration but found infinite duration: $s"))
        }
    )

Let me know
Thanks

[alexarchambault]

@joan38 Sure, that would work!