📝 Add description about ingress

Signed-off-by: Rintaro Okamura <rintaro.okamura@gmail.com>

charts/vald/README.md.gotmpl

@@ -63,4 +63,7 @@ Please run the following command to install the chart with this values yaml,
     $ helm repo add vald https://vald.vdaas.org/charts
     $ helm install --values values-agent-ngt-standalone.yaml vald-agent-ngt vald/vald
 
+If you'd like to access the agents from out of the Kubernetes cluster, it is recommended to create an [Ingress][k8s-ingress].
+
 agent-ngt-standalone-yaml: ./values-agent-ngt-standalone.yaml
+k8s-ingress: https://kubernetes.io/docs/concepts/services-networking/ingress/