feat: added kafka-topic provisioner

[astromechza]

See the newly added example in examples/13-kafka-topic. This provisions a 3-partition kafka topic on a random host.

$ go run ../../cmd/score-compose resources list
dns.default#hello-world.dns
kafka-topic.default#hello-world.bus
route.default#hello-world.route

$ go run ../../cmd/score-compose resources get-outputs 'kafka-topic.default#hello-world.bus'
{"host":"kafka-e9KQfd","name":"topic-lTppsn","num_partitions":3,"port":"9092"}

You can see in the example screenshot that the redpanda console can connect to it successfully:

Fixes #149

[mathieu-benoit]

I'm not familiar with kakfa at all, but is the publishPort really optional? Should we just add this port anyway without having this as an annotation in Score?

[astromechza]

@mathieu-benoit this is about publishing the port outside of docker. It's already available for services to call within the docker network. The reason to make it optional is that it may conflict with other ports open on the host so we need the users concent to start listening on this.

[mathieu-benoit]

LGTM