Add ServiceMonitor (Enhancement)

The helm chart currently adds the well-known prometheus.io/* annotations for metrics scraping.

While this is useful, many clusters have now moved to Prometheus Operator which instead uses ServiceMonitor / PodMonitor CRDs to specify scrape rules. The prometheus team seems to prefer this approach over the annotations (comment). As a result, may helm charts now include the option to create a PodMonitor eg (ingress-nginx) eg (cert-manager) eg (AWS LB Controller).

Would this project be open to the same approach? I would be happy to submit an MR.