docs: Update helm README (#2218)

**NO_CI***

dev/helm/README.md

@@ -53,6 +53,11 @@ It also optionally packages the [PostgreSQL](https://github.com/kubernetes/chart
 
 To install the chart with the release name `my-release` run the following from this (`helm`) directory:
 
+### Using Helm 3:
+```console
+$ helm install my-release .
+```
+### Using Helm 2:
 ```console
 $ helm install --name my-release . 
 ```