Emphasize VPC requirements

examples/from-private-vpc/README.md

@@ -8,6 +8,9 @@ In this example, the VPC is a "private VPC". It contains:
 * private subnets using a NAT gateway for egress. That's where the nodes and pods will go.
 * public subnets. That's where the load balancers and other exposed public IPs will go.
 
+**Please note that the VPC must contain public subnets. 
+Without public subnets, critical features of the platform including notebook support, live Spark UI, and live log streams will be missing.**
+
 Additionally, the VPC must have the following tags to be suitable for an EKS cluster:
 * `kubernetes.io/cluster/<eks-cluster-name> = shared` on the VPC itself, where `<eks-cluster-name>` is the name of the EKS cluster that will use this VPC. This tag should not be necessary since Kubernetes 1.19. We recommend to add it anyway.
 * `kubernetes.io/cluster/<eks-cluster-name> = shared` on all subnets.