housekeeping: Update README.md

[skip ci]

README.md

@@ -39,6 +39,20 @@ Checking for UDP Connectivity with the STUN Server
 
 ![](pic/RFC5780_4.2.png)
 
+### Mapping Behavior
+Determining NAT Mapping Behavior
+
+![](pic/RFC5780_4.3.png)
+
+### Filtering Behavior
+Determining NAT Filtering Behavior
+
+![](pic/RFC5780_4.4.png)
+
+### Combining Tests
+
+![](pic/RFC5780_4.5.png)
+
 ## STUN Server
 ### Docker
 ```

STUN/Client/StunClient5389UDP.cs

@@ -60,7 +60,7 @@ public class StunClient5389UDP : IStunClient
 
 		await FilteringBehaviorTestBaseAsync(cancellationToken);
 		if (State.BindingTestResult is not BindingTestResult.Success
-			|| State.FilteringBehavior == FilteringBehavior.UnsupportedServer
+			|| State.FilteringBehavior is FilteringBehavior.UnsupportedServer
 		   )
 		{
 			return;