Added support in Windows and Android for proxying web requests from the browser through native code to allow for modifying the request, and creating custom responses.

Add proxy support for iOS and Mac. Cleaned up some of the previous proxy code for Android and Windows.

Add round trip invoke JS-.NET-JS by leveraging the proxy framework that was created.

- Bug fix: expose method to get proxy origin in JS. iOS/Mac has a different URL scheme than Android/Windows. Simple helper method gives users JS code the correct URL to the proxy service for the platform the web view is running on.
- A few improvements to better handle errors.
- Document code
- Readme documentation
- Move async invoke samples to methodinvoke.html sample

commit 6bb1c5f
Author: Eilon Lipton <Eilon@users.noreply.github.com>
Date:   Mon Mar 11 11:53:17 2024 -0700

    Update HybridWebViewHandler.MacCatalyst.cs

commit 3b56ebe
Author: Eilon Lipton <Eilon@users.noreply.github.com>
Date:   Mon Mar 11 11:43:19 2024 -0700

    Try to make iOS proxy code async