Resolve "Docs: Add Metrics Report Sample"

doc/ci/metrics_reports.md

@@ -49,3 +49,10 @@ metrics:
     reports:
       metrics: metrics.txt
 ```
+
+## Advanced Example
+
+An advanced example of an OpenMetrics text file (from the [Prometheus documentation](https://github.com/prometheus/docs/blob/master/content/docs/instrumenting/exposition_formats.md#text-format-example))
+renders in the merge request widget as:
+
+![Metrics Reports Advanced](img/metrics_reports_advanced_v13_0.png)