expose touch events in canvas widget

graphics/src/widget/canvas.rs

@@ -173,6 +173,9 @@ where
             iced_native::Event::Mouse(mouse_event) => {
                 Some(Event::Mouse(mouse_event))
             }
+            iced_native::Event::Touch(touch_event) => {
+                Some(Event::Touch(touch_event))
+            }
             iced_native::Event::Keyboard(keyboard_event) => {
                 Some(Event::Keyboard(keyboard_event))
             }

graphics/src/widget/canvas/event.rs

@@ -1,6 +1,7 @@
 //! Handle events of a canvas.
 use iced_native::keyboard;
 use iced_native::mouse;
+use iced_native::touch;
 
 pub use iced_native::event::Status;
 
@@ -12,6 +13,9 @@ pub enum Event {
     /// A mouse event.
     Mouse(mouse::Event),
 
+    /// A touch event.
+    Touch(touch::Event),
+
     /// A keyboard event.
     Keyboard(keyboard::Event),
 }