add link to cex plug-in

Author: SNiemann15

modules/nodes-pods-plugins-about.adoc

@@ -53,6 +53,7 @@ service DevicePlugin {
 * link:https://github.com/NVIDIA/k8s-device-plugin[Nvidia official GPU device plug-in]
 * link:https://github.com/vikaschoudhary16/sfc-device-plugin[Solarflare device plug-in]
 * link:https://github.com/kubevirt/kubernetes-device-plugins[KubeVirt device plug-ins: vfio and kvm]
+* link:https://github.com/ibm-s390-cloud/k8s-cex-dev-plugin[Kubernetes device plug-in for IBM Crypto Express (CEX) cards]
 
 
 [NOTE]