Example: Add basic metrics example with prometheus exporter

[mayurkale22]

Provide an example of how the OpenTelemetry Metrics library can be used to record data in the form of Gauge and/or Counter and export them to prometheus backend using OpenTelemetry Prometheus exporter.

[dyladan]

@mayurkale22 @danielkhan while working on #553 I have created an example that I am using in my testing so please assign this to me.

[mayurkale22]

Closed via #560