book: add documentation regarding storage drivers

Author: cpanato

docs/book/src/topics/external-cloud-provider.md

@@ -23,3 +23,17 @@ kube-system   cloud-node-manager-hbbqt
 kube-system   cloud-node-manager-mfsdg                                            1/1     Running   0          39s
 kube-system   cloud-node-manager-qrz74                                            1/1     Running   0          24s
 ```
+
+## Storage Drivers
+
+### Azure File CSI Driver
+
+To install the Azure File CSI driver please refer to the [installation guide](https://github.com/kubernetes-sigs/azurefile-csi-driver/blob/master/docs/install-azurefile-csi-driver.md)
+
+Repository: https://github.com/kubernetes-sigs/azurefile-csi-driver
+
+### Azure Disk CSI Driver
+
+To install the Azure Disk CSI driver please refer to the [installation guide](https://github.com/kubernetes-sigs/azuredisk-csi-driver/blob/master/docs/install-azuredisk-csi-driver.md)
+
+Repository: https://github.com/kubernetes-sigs/azuredisk-csi-driver