I wonder if this will actually happen, since most webviews are closed source and the work of big corporations? Maybe people like the Electron maintainers can get involved.
• WKWebView (iOS, macOS): https://github.com/WebKit/webkit/blob/main/Source/WebKit/UIP...
• Android WebView: https://android.googlesource.com/platform/frameworks/base/+/...
• Mozilla GeckoView: https://github.com/mozilla/gecko-dev/tree/master/mobile/andr...
• Chromium Embedded Framework (CEF): https://bitbucket.org/chromiumembedded/cef/src/master/
The main ones that aren't open source are the Windows WebView and WebView2 components.