Change UIWebView (deprecated since iOS 12.0) to WKWebView

[jstuth]

This pr removes the need of the deprecated UIWebView on iOS 8.0+ and uses the WKWebView instead as noted in the official UIWebView documentation:

Note

In apps that run in iOS 8 and later, use the WKWebView class instead of using UIWebView. Additionally, consider setting the WKPreferences property javaScriptEnabled to false if you render files that are not supposed to run JavaScript.

see: https://developer.apple.com/documentation/uikit/uiwebview

[j0j00]

Thanks for the PR, will try and push an update now.