touch click support

[nicolasavru]

Is there any way to get touch "clicks" (equivalent of mouse button clicks)? I'm adding and removing map markers based on clicks on the map. That works fine on linux and in a desktop browser with wasm, but doesn't work on a mobile browser. UserEvent doesn't have a touch enum variant and the touches aren't being translated to mouse events either. Winit seems to support it fine as I can interact with egui widgets.