WebSocketClientHandshaker: add public accessors for parameters (#13009)

Motivation:

Websocket client & server handshakers may be extended with custom frame encoder / decoder,
however client handshaker parameters are private so cant be accessed by custom frame encoder / decoder.

Modifications:

WebSocketClientHandshaker: add public accessors for parameters.

Result:

Custom frame encoder / decoder may be provided with websocket client handshaker parameters

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketClientHandshaker13.java

@@ -346,4 +346,15 @@ public WebSocketClientHandshaker13 setForceCloseTimeoutMillis(long forceCloseTim
         return this;
     }
 
+    public boolean isAllowExtensions() {
+        return allowExtensions;
+    }
+
+    public boolean isPerformMasking() {
+        return performMasking;
+    }
+
+    public boolean isAllowMaskMismatch() {
+        return allowMaskMismatch;
+    }
 }