message: Add example to `iced_native::UserInterface`
diff: @@ -12,6 +12,13 @@ use std::hash::Hasher;
  /// charge of using this type in your system in any way you want.
  ///
  /// [`Layout`]: struct.Layout.html
  +///
  +/// # Example
  +/// The [`integration` example] uses a [`UserInterface`] to integrate Iced in
  +/// an existing graphical application.
  +///
  +/// [`integration` example]: https://github.com/hecrj/iced/tree/0.1/examples/integration
  +/// [`UserInterface`]: struct.UserInterface.html
  #[allow(missing_debug_implementations)]
  pub struct UserInterface<'a, Message, Renderer> {
  hash: u64,
  