doc: quick note about logging

Author: ldez

readme.md

@@ -183,6 +183,12 @@ func (e *Example) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 }
 ```
 
+## Logs
+
+Currently, the only way to send logs to Traefik is to use `os.Stdout.WriteString("...")` or `os.Stderr.WriteString("...")`.
+
+In the future, we will try to provide something better and based on levels.
+
 ## Plugins Catalog
 
 Traefik plugins are stored and hosted as public GitHub repositories.