Update customization.md HidePort (#326)

Author: ianb-mp

website/docs/guide/customization.md

@@ -76,6 +76,10 @@ a custom logger using `Echo#Logger`.
 
 `Echo#HideBanner` can be used to hide the startup banner.
 
+## Listener Port
+
+`Echo#HidePort` can be used to hide the listener port message.
+
 ## Custom Listener
 
 `Echo#*Listener` can be used to run a custom listener.
@@ -134,4 +138,4 @@ Have a look at `DefaultJSONSerializer` on [json.go](https://github.com/labstack/
 
 `Echo#HTTPErrorHandler` can be used to register a custom http error handler.
 
-[Learn more](./error-handling.md)
+[Learn more](./error-handling.md)