docs(ckpt): add new how-to in menu (#5226)

Author: nerda-codes

menu/navigation.json

@@ -3731,6 +3731,10 @@
                     "label": "Send metrics and logs to your Cockpit",
                     "slug": "send-metrics-logs-to-cockpit"
                   },
+                  {
+                    "label": "Federate Scaleway metrics with your own Prometheus",
+                    "slug": "federate-scaleway-metrics"
+                  },
                   {
                     "label": "Delete a custom data source",
                     "slug": "delete-external-data-sources"