Add Shutting down section for cleanup steps

example/otel-collector/README.md

@@ -53,3 +53,11 @@ web-browser to view the generated traces.
 The Prometheus UI is available at
 [http://localhost:9090](http://localhost:9090). Navigate there in your favorite
 web-browser to view the generated metrics.
+
+# Shutting down
+
+To shut down and clean the example, run
+
+```bash
+docker compose down
+```