Add documentation for example service monitoring

manifests/examples/example-app/prometheus-frontend-svc.yaml

@@ -2,6 +2,7 @@ apiVersion: v1
 kind: Service
 metadata:
   name: prometheus-frontend
+  namespace: default
 spec:
   type: NodePort
   ports:

manifests/examples/example-app/prometheus-frontend.yaml

@@ -2,6 +2,7 @@ apiVersion: prometheus.coreos.com/v1alpha1
 kind: Prometheus
 metadata:
   name: prometheus-frontend
+  namespace: default
   labels:
     prometheus: frontend
 spec:

manifests/examples/example-app/servicemonitor-frontend.yaml

@@ -2,6 +2,7 @@ apiVersion: prometheus.coreos.com/v1alpha1
 kind: ServiceMonitor
 metadata:
   name: frontend
+  namespace: default
   labels:
     team: frontend
 spec: