Adjust height of WKWebView frame based on scrollHeight of the webView's content

WKWebViewSizeToFit.swift

// Since the WKWebView has no sizeToFit() method, increase the frame height of the webView to 
// match the height of the content's scrollHeight
// 
// The WKWebView's `navigationDelegate` property needs to be set for the delegate method to be called

func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {

    if webView.isLoading == false {
        webView.evaluateJavaScript("document.body.scrollHeight", completionHandler: { [weak self] (result, error) in
            if let height = result as? CGFloat {
                webView.frame.size.height += height
            }
        })
    }

}