Improve tlsConfig Monitoring docs

Orig. request by Vivek Yoganand <vyoganan@redhat.com>:

How a service is monitored using HTTPS TLS "tlsconfig"? Steps to do tlsconfig; Missed in the below document
https://docs.openshift.com/container-platform/4.8/monitoring/managing-metrics.html

[Pasted for more visibility]
In OpenShift Container Platform 4.8, you can use the tlsConfig property for a ServiceMonitor resource to specify the TLS configuration to use when scraping metrics from an endpoint. The tlsConfig property is not yet available for PodMonitor resources. If you need to use a TLS configuration when scraping metrics, you must use ServiceMonitor resource.
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Paul Needle:

It would be better to ask the Monitoring team what the current recommendations are for any new documentation requirements, given that support consideration and that the module is three years old.

In the live docs, there is the Querying metrics for user-defined projects as a developer section, which provides some guidance on custom PromQL queries. I'm not sure if that helps with the requirement here.

There is some similar guidance in Querying metrics for all projects as a cluster administrator for core OpenShift projects too.

It might be worth reading through the Managing metrics page and then if there are further requirements they could be added to that assembly.
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Initial task:

Describe how to use the tlsConfig property with ServiceMonitor.