winit-core:winit: add tablet input support

The API is integrated into the `WindowEvent::Pointer*` API and is
present in form of `TabletTool` variant on corresponding data entries.

For now implemented for Web, Windows, and with limitations for Wayland.

Fixes #99.

Co-authored-by: daxpedda <daxpedda@gmail.com>

winit-uikit/src/view.rs

@@ -461,6 +461,10 @@ impl WinitView {
         let window = self.window().unwrap();
         let mut touch_events = Vec::new();
         for touch in touches {
+            if let UITouchType::Pencil = touch.r#type() {
+                continue;
+            }
+
             let logical_location = touch.locationInView(None);
             let touch_type = touch.r#type();
             let force = if let UITouchType::Pencil = touch_type {