Add a `object` combinator

[Schniz]

The basic should be the same as command, and maybe command should use it internally:

object({
  someName: ArgParser<T>,
  otherName: ArgParser<R>,
}) => ArgParser<{ someName: T, otherName: R }>

[Schniz]

I have implemented it. Wasn't hard. But I'm not sure that it is far better than:

const extended = {
  someName: myParser(),
  otherName: otherName(),
} as const

command({
  args: { ...extended }
  ...
})

Maybe I will do it just for the sake of single responsibility, the command function is fairly large. Extracting the object parsing into an object would kinda make sense for maintainability.