add doc

website/docs/d/virtual_network_gateway_connection.html.markdown

@@ -72,6 +72,10 @@ output "virtual_network_gateway_connection_id" {
     Only a single policy can be defined for a connection. For details on
     custom policies refer to [the relevant section in the Azure documentation](https://docs.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-ipsecikepolicy-rm-powershell).
 
+* `traffic_selector_policy` (Optional) A `traffic_selector_policy` which allows to specify traffic selector policy proposal to be used in a virtual network gateway connection.
+    Only one block can be defined for a connection.
+    For details about traffic selectors refer to [the relevant section in the Azure documentation](https://docs.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-connect-multiple-policybased-rm-ps).
+
 * `tags` - A mapping of tags to assign to the resource.
 
 The `ipsec_policy` block supports:
@@ -102,6 +106,12 @@ The `ipsec_policy` block supports:
 * `sa_lifetime` - The IPSec SA lifetime in seconds. Must be at least
     `300` seconds.
 
+The `traffic_selector_policy` block supports:
+
+* `local_address_cidrs` - List of local CIDRs.
+
+* `remote_address_cidrs` - List of remote CIDRs.
+
 ## Timeouts
 
 The `timeouts` block allows you to specify [timeouts](https://www.terraform.io/docs/configuration/resources.html#timeouts) for certain actions: