Apache Kafka Streaming with PyFlink

## About
[apache-kafka-flink-streaming](https://github.com/crate/cratedb-examples/tree/main/application/apache-kafka-flink-streaming) has a nice new example contributed by @surister. Thanks!

## Backlog
- [ ] Add a GHA workflow recipe, and add the outcome to the [build status page](https://cratedb.com/docs/crate/clients-tools/en/latest/status.html).
- [ ] Add an item to the [integration tutorials section about Apache Flink](https://cratedb.com/docs/guide/integrate/etl/index.html#apache-flink).

/cc @matkuliak