Add japan, korea, and eastus2/centralus regions.

Author: wmgries

articles/storage/files/understanding-billing.md

@@ -131,6 +131,12 @@ Currently, these SKUs are generally available in a limited subset of regions:
 - North Central US
 - West US
 - East US
+- Japan East
+- Japan West
+- Korea Central
+- Korea South
+- East US 2
+- Central US
 
 ### Provisioned v2 provisioning detail
 When you create a provisioned v2 file share, you specify the provisioned capacity for the file share in terms of storage, IOPS, and throughput. File shares are limited based on the following attributes: