message: Fix `multitouch` example
diff: //! a circle around each fingertip. This only works on touch-enabled
  //! computers like Microsoft Surface.
  use iced::widget::canvas::event;
  -use iced::widget::canvas::{self, Canvas, Cursor, Geometry, Stroke};
  +use iced::widget::canvas::stroke::{self, Stroke};
  +use iced::widget::canvas::{self, Canvas, Cursor, Geometry};
  use iced::{
  executor, touch, window, Application, Color, Command, Element, Length,
  Point, Rectangle, Settings, Subscription, Theme,
  @@ -186,7 +187,7 @@ impl canvas::Program<Message> for State {
  frame.stroke(
  &path,
  Stroke {
  - color: Color::BLACK,
  + style: stroke::Style::Solid(Color::BLACK),
  width: 3.0,
  ..Stroke::default()
  },
  