docs: add note to Controller documentation

Author: mbrowne

src/content/docs/usecontroller/controller.mdx

@@ -8,6 +8,8 @@ sidebar: apiLinks
 
 React Hook Form embraces uncontrolled components and native inputs, however it's hard to avoid working with external controlled component such as [React-Select](https://github.com/JedWatson/react-select), [AntD](https://github.com/ant-design/ant-design) and [MUI](https://mui.com/). This wrapper component will make it easier for you to work with them.
 
+**Note:** if you simply want to control a field's value from outside the form, it's not necessary to use `Controller`. You can simply use the [`values`](/docs/useform#values) option of `useForm`.
+
 ### Props
 
 ---