Playing around with kafka

• @confluentinc/kafka-javascript has a couple of compatibility modes, described here. tl;dr it works on basically anything, but if it doesn't work for some reason you'll need to install librdkafka and set up a keyring.
• Kafka > v3.3 introduced KRaft, and in doing so deprecated zookeeper. I've left an additional compose file docker-compose-zookeeper.yml that includes it, just because.