Adding Missing cmd to add helm repo (#5977)

Signed-off-by: Swapnil Kulkarni <[email protected]>

Author: meswapnilk

content/en/docs/kubernetes/helm/demo.md

@@ -24,6 +24,12 @@ and detailed descriptions can be found in the
 
 ## Installation
 
+Add OpenTelemetry Helm repository:
+
+```shell
+helm repo add open-telemetry https://open-telemetry.github.io/opentelemetry-helm-charts
+```
+
 To install the chart with the release name `my-otel-demo`, run the following
 command: