Clarify comment for Addhandler and multiple topics (#551)

Co-authored-by: Miłosz Smółka <[email protected]>

Author: addshore

message/router.go

@@ -265,7 +265,7 @@ func (d DuplicateHandlerNameError) Error() string {
 //
 // publishTopic is a topic to which router will produce messages returned by handlerFunc.
 // When handler needs to publish to multiple topics,
-// it is recommended to just inject Publisher to Handler or implement middleware
+// it is recommended to use AddNoPublisherHandler and inject a Publisher or implement middleware
 // which will catch messages and publish to topic based on metadata for example.
 //
 // If handler is added while router is already running, you need to explicitly call RunHandlers().