Callback to decide if a certain URL should be loaded

iOS has [webView:shouldStartLoadWithRequest:navigationType:](https://developer.apple.com/documentation/uikit/uiwebviewdelegate/1617945-webview?language=objc) which can be used to deny loading if you don't want to follow a URL.

One of the possible uses: This could be used to communicate some state from within the webview. You parse the request and deny loading so the current page stays the same.