Update readme info regarding WebAssembly and web target (#1726)

README.md

@@ -71,13 +71,24 @@ Winit provides the following features, which can be enabled in your `Cargo.toml`
 
 #### WebAssembly
 
-Building a binary will yield a `.js` file. In order to use it in an HTML file, you need to:
+Winit supports compiling to the `wasm32-unknown-unknown` target with either a
+`stdweb` or a `web-sys` backend for use on web browsers. However, please note
+that **the `stdweb` backend is being deprecated and may be removed in a future
+release of Winit**. The `web-sys` backend is also more feature complete.
 
-- Put a `<canvas id="my_id"></canvas>` element somewhere. A canvas corresponds to a winit "window".
+On the web platform, a Winit window is backed by a `<canvas>` element. You can
-- Write a Javascript code that creates a global variable named `Module`. Set `Module.canvas` to
+either [provide Winit with a `<canvas>` element][web with_canvas], or [let Winit
-  the element of the `<canvas>` element (in the example you would retrieve it via `document.getElementById("my_id")`).
+create a `<canvas>` element which you can then retrieve][web canvas getter] and
-  More information [here](https://kripken.github.io/emscripten-site/docs/api_reference/module.html).
+insert it into the DOM yourself.
-- Make sure that you insert the `.js` file generated by Rust after the `Module` variable is created.
+
+For example code using Winit with WebAssembly, check out the [web example]. For
+information on using Rust on WebAssembly, check out the [Rust and WebAssembly
+book].
+
+[web with_canvas]: https://docs.rs/winit/latest/wasm32-unknown-unknown/winit/platform/web/trait.WindowBuilderExtWebSys.html#tymethod.with_canvas
+[web canvas getter]: https://docs.rs/winit/latest/wasm32-unknown-unknown/winit/platform/web/trait.WindowExtWebSys.html#tymethod.canvas
+[web example]: ./examples/web.rs
+[Rust and WebAssembly book]: https://rustwasm.github.io/book/
 
 #### Android