feat: add k8s_gateway for accessing ingresses locally over DNS (#287)

tmpl/cluster/cluster-settings.yaml

@@ -6,4 +6,5 @@ metadata:
   namespace: flux-system
 data:
   METALLB_LB_RANGE: ${BOOTSTRAP_METALLB_LB_RANGE}
+  METALLB_K8S_GATEWAY_ADDR: ${BOOTSTRAP_METALLB_K8S_GATEWAY_ADDR}
   METALLB_TRAEFIK_ADDR: ${BOOTSTRAP_METALLB_TRAEFIK_ADDR}