Add attribute reference to google_service_networking_connection (#5679) (#4034)

Co-authored-by: Cameron Thornton <[email protected]>
Signed-off-by: Modular Magician <[email protected]>

Co-authored-by: Cameron Thornton <[email protected]>

Author: modular-magician

.changelog/5679.txt

@@ -0,0 +1,2 @@
+```release-note:none
+```

website/docs/r/service_networking_connection.html.markdown

@@ -50,6 +50,13 @@ The following arguments are supported:
   this service provider. Note that invoking this method with a different range when connection
   is already established will not reallocate already provisioned service producer subnetworks.
 
+## Attributes Reference
+
+In addition to the arguments listed above, the following computed attributes are exported:
+
+* `peering` - (Computed) The name of the VPC Network Peering connection that was created by the service producer.
+
+
 ## Import
 ServiceNetworkingConnection can be imported using any of these accepted formats