Draft web platform structure

src/platform/web.rs

@@ -0,0 +1,15 @@
+#[cfg(feature = "stdweb")]
+use stdweb::web::html_element::CanvasElement;
+
+#[cfg(feature = "stdweb")]
+pub trait WindowExtStdweb {
+    fn canvas(&self) -> CanvasElement;
+}
+
+#[cfg(feature = "web-sys")]
+use web_sys::HtmlCanvasElement;
+
+#[cfg(feature = "web-sys")]
+pub trait WindowExtWebSys {
+    fn canvas(&self) -> HtmlCanvasElement;
+}