Link to HttpClientFactory doco

Link to new HttpClientFactory doco from readme

README.md

@@ -43,6 +43,10 @@ Polly offers multiple resilience policies:
 
 In addition to the detailed pages on each policy, an [introduction to the role of each policy in resilience engineering](https://github.com/App-vNext/Polly/wiki/Transient-fault-handling-and-proactive-resilience-engineering)  is also provided in the wiki.
 
+### Using Polly with HttpClient factory from ASPNET Core 2.1
+
+For using Polly with  HttpClient factory from ASPNET Core 2.1, see our [detailed wiki page](https://github.com/App-vNext/Polly/wiki/Polly-and-HttpClientFactory), then come back here or [explore the wiki](https://github.com/App-vNext/Polly/wiki) to learn more about the operation of each policy.
+
 # Usage – fault-handling policies
 
 Fault-handling policies handle specific exceptions thrown by, or results returned by, the delegates you execute through the policy.