Add doc blocks for new options.

src/View/Helper/FormHelper.php

@@ -320,11 +320,14 @@ protected function _isRequiredField($validationRules)
      *
      * - `type` Form method defaults to autodetecting based on the form context. If
      *   the form context's isCreate() method returns false, a PUT request will be done.
+     * - `method` Set the form's method attribute explicitly.
      * - `action` The controller action the form submits to, (optional). Use this option if you
      *   don't need to change the controller from the current request's controller. Deprecated since 3.2, use `url`.
      * - `url` The URL the form submits to. Can be a string or a URL array. If you use 'url'
      *    you should leave 'action' undefined.
      * - `encoding` Set the accept-charset encoding for the form. Defaults to `Configure::read('App.encoding')`
+     * - `enctype` Set the form encoding explicitly. By default `type => file` will set `enctype`
+     *   to `multipart/form-data`.
      * - `templates` The templates you want to use for this form. 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.