Add info about "templates" option for FormHelper::input().

src/View/Helper/FormHelper.php

@@ -978,6 +978,9 @@ public function fieldset($fields = '', array $options = [])
      * - `nestedInput` - Used with checkbox and radio inputs. Set to false to render inputs outside of label
      *   elements. Can be set to true on any input to force the input inside the label. If you
      *   enable this option for radio buttons you will also need to modify the default `radioWrapper` template.
+     * - `templates` - The templates you want to use for this input. Any templates will be merged on top of
+     *   the already loaded templates. This option can either be a filename in /config that contains
+     *   the templates you want to load, or an array of templates to use.
      *
      * @param string $fieldName This should be "modelname.fieldname"
      * @param array $options Each type of input takes different options.