Option's default value is not tested against validator

[sergei-dyshel]

I would expect TS compiler to warn me when defining e.g.:

  choice = Option.String("--choice", "d", {
    description: "Choice option",
    validator: t.isEnum(["a", "b", "c"] as const),
  });

that "d" does not pass validation, resulting in this error during runtime:

Usage Error: Invalid value for choice: expected one of "a", "b", or "c" (got "d"