Mention new feature for alerting on common k8s issues (#92)

* updated to new builtin:kubernetes metrics

* updated metric expressions to new k8s metrics; removed unnecessary brackets; some polishing

* formating

* mention new feature for alerting on common k8s issues

* Update metric-expressions-for-k8s.md

metric-example/metric-expressions-for-k8s.md

@@ -1,6 +1,9 @@
 # Metric Expressions for K8s
 This document collects frequently asked metric expressions for typical K8s use-cases. Listed metric expressions can be used for [charting](https://www.dynatrace.com/support/help/how-to-use-dynatrace/dashboards-and-charts/explorer/explorer-advanced-query-editor/) or alerting using [custom metric events](https://www.dynatrace.com/support/help/how-to-use-dynatrace/problem-detection-and-analysis/problem-detection/metric-events-for-alerting/advanced-metric-queries/).
 
+# Important note on alerting
+If your main use case is to **alert on common Kubernetes issues**, please **do not** set up *Metric events* using any of the metric expressions below. **Instead**, use our product's **built-in alerts**, which we introduced with version 1.254. You find them in **Settings** > **Anomaly detection** > **Kubernetes**. You can find more information about this feature in our [documentation](https://www.dynatrace.com/support/help/how-to-use-dynatrace/infrastructure-monitoring/container-platform-monitoring/kubernetes-monitoring) and in our [community](https://community.dynatrace.com/t5/Feedback-channel/Introducing-easy-alerting-on-common-Kubernetes-platform-issues/td-p/197824).
+
 **Table of contents**
 
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