Javascript bridge window.external.notify

Add a sample demonstrating best practice to communicate events between the host and javascript both ways.

An messaging abstraction would benefit the WebView2 spec. There is a supported 'WebMessageReceived' API but is only from Host originated events which await a JS response.

The WebView2_spec says: "WebMessageReceived – Occurs when the content contained in the WebView2 control passes a string to the application by using JavaScipt."
a sample showing how to send messages from JavaScript to the Native application hosting the WebView would be very useful.

"Win32 WebViewControl did not support ObjectForScripting or AddWebAllowedObject", @rjmurillo made a fine example of a necessary workaround to create a Javascript to Natvie notification 'JavaScriptBridge'.

It's basis was :

window.external.notify(event.data);

The browser MDN web docs on Window.external say it is deprecated. What would be the Chrome equivalent?

An iOS Safari webView compatible example:
https://github.com/lovesunstar/WKBridge/blob/fb30c123e68b4dcd4c4a2a8087d7383dbac0afe9/Example/WKBridge/test.html

Start with the WebView2_spec WebMessageReceived section and the referenced JavaScriptBridge/Bridge.html example, then inspect the repository for an existing WebView2 sample entry point. Define a supported sample that demonstrates host-to-JavaScript and JavaScript-to-native event communication, with completion verified by both directions working without relying on the deprecated window.external API.