add screenshot for fastpath with vnet peering:

Author: duongau

articles/expressroute/about-fastpath.md

@@ -30,6 +30,8 @@ To configure FastPath, the virtual network gateway must be either:
 
 ### Virtual network peering
 
+:::image type="content" source=".\media\about-fastpath\fastpath-vnet-peering.png" alt-text="Diagram of an ExpressRoute connection with Fastpath and virtual network peering.":::
+
 For the FastPath feature to function correctly, the hub virtual network and any peered spoke virtual networks must reside within the same region. It is important to note that FastPath doesn't support globally peered virtual networks.
 
 ## Limitations