consume callback has an incorrect typing

[abarisain]

Environment Information

• node-rdkafka version [e.g. 2.3.3]: 2.18.0

Steps to Reproduce

Use .consume(callback) from typescript. Type of "messages" in the callback is Message[] while the lib returns a single message. I have to force cast it to use it:

consumer.consume((err, msg) => {
  const message = msg as unknown as RDKafka.Message;

The .consume variant with two parameters is alright