Add the following support versions to content/en/docs/concepts/storage/storage-classes.md

here is support/version matrix of various volume types look like:

EBS (1.11)
Cinder (1.11)
Glusterfs (1.11)
GCE PD (1.11)
Portworx (1.11)
Azure File (1.11)
RBD (1.11)
Azure Disk(1.11)
Flex Volume (1.13)
CSI (1.14, 1.15 - Alpha, 1.16 beta)

It might be worth updating this document and explicitly specify which version of k8s the volume plugin type supported expansion.