Specify service-cluster-ip-range for apiserver

Author: kvaps

content/en/docs/concepts/services-networking/dual-stack.md

@@ -47,6 +47,7 @@ To enable IPv4/IPv6 dual-stack, enable the `IPv6DualStack` [feature gate](/docs/
 
    * kube-apiserver:
       * `--feature-gates="IPv6DualStack=true"`
+      * `--service-cluster-ip-range=<IPv4 CIDR>,<IPv6 CIDR>`
    * kube-controller-manager:
       * `--feature-gates="IPv6DualStack=true"`
       * `--cluster-cidr=<IPv4 CIDR>,<IPv6 CIDR>`