chore: update req_config.md with absolute URI config (#239)

Author: jasonsaayman

posts/en/req_config.md

@@ -22,6 +22,11 @@ These are the available config options for making requests. Only the `url` is re
   // to methods of that instance.
   baseURL: 'https://some-domain.com/api',
 
+  // `allowAbsoluteUrls` determines whether or not absolute URLs will override a configured `baseUrl`.
+  // When set to true (default), absolute values for `url` will override `baseUrl`.
+  // When set to false, absolute values for `url` will always be prepended by `baseUrl`.
+  allowAbsoluteUrls: true,
+
   // `transformRequest` allows changes to the request data before it is sent to the server
   // This is only applicable for request methods 'PUT', 'POST', 'PATCH' and 'DELETE'
   // The last function in the array must return a string or an instance of Buffer, ArrayBuffer,