update to new decode api

[dvic]

Are there any plans to upgrade to the new decode API? I could try to tackle this :)

functions like this

pub fn non_negative_int(dynamic: Dynamic) -> Result(Int, List(DecodeError)) {
  use int <- result.try(dynamic.int(dynamic))

  case int >= 0 {
    True -> Ok(int)
    False ->
      Error([
        DecodeError(
          expected: "A non-negative int",
          found: int.to_string(int),
          path: [],
        ),
      ])
  }
}

would become split into two:

pub fn non_negative_int(dynamic: Dynamic) -> Result(Int, List(DecodeError)) {
  decode.run(dynamic, non_negative_int_decoder())
}

pub fn non_negative_int_decoder() -> Decoder(Int) {
  use int <- decode.then(decode.int)

  case int >= 0 {
    True -> decode.success(int)
    False -> decode.failure(0, "A non-negative int")
  }
}

This is a breaking change in the sense that the DecodeError type changes (dynamic.DecodeError vs decode.DynamicError).

Or would you rather just keep the function but change the signature (i.e., return a Decoder(a)). This would of course be a larger breaking change but I'm fine with that as well :)