On Web, implement Send and Sync where appropriate (#2834)

examples/web_aspect_ratio.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::disallowed_methods)]
+
 pub fn main() {
     println!("This example must be run with cargo run-wasm --example web_aspect_ratio")
 }
@@ -66,7 +68,7 @@ This example demonstrates the desired future functionality which will possibly b
         let body = document.body().unwrap();
 
         // Set a background color for the canvas to make it easier to tell the where the canvas is for debugging purposes.
-        let canvas = window.canvas();
+        let canvas = window.canvas().unwrap();
         canvas
             .style()
             .set_css_text("display: block; background-color: crimson; margin: auto; width: 50%; aspect-ratio: 4 / 1;");