is it possible to have one-master(r/w node) and multiple slave(read nodes) ?

I am wondering whether this operator provides a single master cluster with multiple read replicas, if yes then how to enable it?

Yes, the K8S operator provides a pod with ProxySQL which is automatically configured to treat your 3-node PXC much like a source/replica setup. There’s nothing to enable; it’s the default. Just make sure your apps are connecting through the proxysql pod.