Update REST.php

As promised at Codeception/lib-innerbrowser#15 (comment) :-)

Author: ThomasLandauer

src/Codeception/Module/REST.php

@@ -430,6 +430,12 @@ public function amAWSAuthenticated($additionalAWSConfig = [])
      *          'tmp_name' => codecept_data_dir('sample_file.pdf')
      *     ]
      * ]);
+     * // Some frameworks (e.g. Symfony) create field names in the form of an "array": `<input type="text" name="form[task]">`
+     * // In this case you need to pass the fields like this:
+     * $I->sendPOST('/add-task', ['form' => [
+     *     'task' => 'lorem ipsum',
+     *     'category' => 'miscellaneous',
+     * ]]);
      * ```
      *
      * @param $url