📝 Warn to use a custom until function to avoid retrying on 4xx errors

Should solve #176

README.md

@@ -653,6 +653,13 @@ const w = wretch().middlewares([retry(), dedupe()])
 
 **Retries a request multiple times in case of an error (or until a custom condition is true).**
 
+> **💡 By default, the request will be retried if the response status is not in the 2xx range.**
+>
+> ```js
+> // Replace the default condition with a custom one to avoid retrying on 4xx errors:
+> until: (response, error) => response && (response.ok || (response.status >= 400 && response.status < 500))
+> ```
+
 ```js
 import wretch from 'wretch'
 import { retry } from 'wretch/middlewares'