Let Helm deploy Kafka-Lag-Exporter's ServiceMonitor

According to https://github.com/lightbend/kafka-lag-exporter, it looks like Helm could install the ServiceMonitor for us.

added modul/theodolite label

@stu126940 Could you have a look on this? It's not urgent, but since you're restarting your cluster regularly, I thought you may could give it a try.

mentioned in merge request !17 (merged)

closed via merge request !17 (merged)

mentioned in commit e202d48e