Adding vShpere volume section to Volumes doc

This documentation is being added in reference to vSphere cloud provider
support work (issue #23932)

docs/user-guide/volumes.md

@@ -69,6 +69,7 @@ Kubernetes supports several types of Volumes:
    * `persistentVolumeClaim`
    * `downwardAPI`
    * `azureFileVolume`
+   * `vsphereVirtualDisk`
 
 We welcome additional contributions.
 
@@ -379,6 +380,44 @@ into a Pod.
 
 More details can be found [here](https://github.com/kubernetes/kubernetes/tree/{{page.githubbranch}}/examples/azure_file/README.md)
 
+### vsphereVirtualDisk
+
+A `VSphereVirtualDisk` is used to mount a vSphere VMDK Volume into your Pod.  The contents
+of a volume are preserved when it is unmounted.
+
+__Important: You must create a VMDK volume using `vmware-vdiskmanager -c` or
+the VSphere API before you can use it__
+
+#### Creating a VMDK volume
+
+Before you can use a vSphere volume with a pod, you need to create it.
+
+```shell
+vmware-vdiskmanager -c -t 0 -s 40GB -a lsilogic myDisk.vmdk
+```
+
+#### vSphere VMDK Example configuration
+
+```yaml
+apiVersion: v1
+kind: Pod
+metadata:
+  name: test-vmdk
+spec:
+  containers:
+  - image: gcr.io/google_containers/test-webserver
+    name: test-container
+    volumeMounts:
+    - mountPath: /test-vmdk
+      name: test-volume
+  volumes:
+  - name: test-volume
+    # This VMDK volume must already exist.
+    vsphereVirtualDisk:
+      volumePath: myDisk
+      fsType: ext4
+```
+
 ## Resources
 
 The storage media (Disk, SSD, etc) of an `emptyDir` volume is determined by the