[WebView] Add support for `ScriptNotify`

[jeromelaban]

What would you like to be added:

Support WebView.ScriptNotify

Why is this needed:

For which Platform:

• [x] iOS
• [x] Android
• [x] WebAssembly
• [ ] WebAssembly renderers for Xamarin.Forms
• [x] macOS
• [ ] Windows
• [ ] Build tasks
• [ ] Solution Templates

Anything else we need to know?

[ToddGlodek]

Does this documentation as of 21SEP2020 indicate that this feature was add/works. (https://platform.uno/docs/articles/implemented/windows-ui-xaml-controls-webview.html) ?? Am I reading it wrong that it is WASM supported.

I installed nuGet package v (3.1.0-dev.416 of Wednesday, September 23, 2020 (9/23/2020) ); and it works in fine in UPW, but I cant get it to do anything in WASM. It doesn't even seen to give any indication that it loaded in the layout.

please advise

WebView : FrameworkElement (UWP) Control (Android/iOS/WASM/MacOS)

[jeromelaban]

@ToddGlodek the WebView control is not yet implemented for WebAssembly (#329) and the documentation needs to be adjusted for WebAssembly. Yet in general doing interop with javascript is generally what's needed: https://platform.uno/docs/articles/interop/wasm-javascript-1.html.

If you have a specific scenario in mind that does not work with Uno, let us know with an additional issue.

Embedding Existing JavaScript Components Into Uno-WASM - Part 1

[MartinZikmund]

This can be implemented in a similar manner as bi-directional communication in WebView2 (even reusing most of the logic)

[ToddGlodek]

Thanks - I'll try it out immediately...!!

[MartinZikmund]

Thanks - I'll try it out immediately...!!

@ToddGlodek just to avoid confusion - I meant the ScriptNotify method in Uno can be later implemented this way, but if you want to do something like this in current stable Uno Platform version, then swap the WebView for WebView2 and follow the docs on the two-way communication