feature request: return output from action handler

[scarf005]

import { Command } from "https://deno.land/x/cliffy@v1.0.0-rc.3/command/mod.ts"

const { output } = await new Command().action(() => 1).parse()
console.log(output) // 1

afaik there's no way to retrieve return value from function passed to Command.action. being able to retrieve (and possibly typecheck its return type) would be useful.