docs: update metrics info for site

site/content/en/docs/reference/metrics.md

@@ -11,6 +11,10 @@ description: >
 JobSet exposes [prometheus](https://prometheus.io) metrics to monitor the health
 of the controller.
 
+## Installation Examples
+
+The following [example](https://github.com/kubernetes-sigs/jobset/tree/main/examples/prometheus-operator) show how to install the Prometheus Operator for JobSet system.
+
 ## JobSet controller health
 
 Use the following metrics to monitor the health of the jobset controller:
@@ -19,3 +23,12 @@ Use the following metrics to monitor the health of the jobset controller:
 | ----------- | ---- | ----------- | ------ |
 | `controller_runtime_reconcile_errors_total` | Counter | The total number of reconciliation errors encountered by each controller. | `controller`: name of controller (i.e. use value `jobset` to obtain metrics for jobset controller) |
 | `controller_runtime_reconcile_time_seconds` | Histogram | The latency of a reconciliation attempt in seconds. | `controller`: name of controller (i.e. use value `jobset` to obtain metrics for jobset controller) |
+
+## JobSet metrics
+
+Use the following metrics to monitor the health of the jobsets created by the jobset controller:
+
+| Metric name                                 | Type | Description                                                               | Labels                                                                                            |
+|---------------------------------------------| ---- |---------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------|
+| `jobset_failed_total`                       | Counter | The total number of failed JobSets. | `jobset_name`: name of jobset      |
+| `jobset_completed_total`                    | Counter | The total number of completed JobSets.                                    | `jobset_name`: name of jobset  |