Enhance documentation on Application Gateway features

Added a tip about Application Gateway DNS resolution and clarified feature configurations.

Author: SebastianClaesson

articles/application-gateway/application-gateway-private-deployment.md

@@ -32,6 +32,9 @@ Application Gateway v2 can now address each of these items to further eliminate
 * Ability to override the default route to the Internet (0.0.0.0/0)
 * DNS resolution via defined resolvers on the virtual network [Learn more](../virtual-network/manage-virtual-network.yml#change-dns-servers), including private link private DNS zones.
 
+>[!Tip]
+>Learn more about Application Gateway DNS resolution at https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-dns-resolution#gateways-with-private-ip-address-only-networkisolationenabled-true
+
 Each of these features can be configured independently. For example, a public IP address can be used to allow traffic inbound from the Internet and you can define a **_Deny All_** outbound rule in the network security group configuration to prevent data exfiltration.
 
 ## Onboard to the feature