Prevent web view flashing white when in loading in dark mode

Reader/Screens/Read/ReadViewController.swift

@@ -52,6 +52,9 @@ class ReadViewController: UIViewController {
         webView.translatesAutoresizingMaskIntoConstraints = false
         webView.navigationDelegate = self
         webView.uiDelegate = self
+        // transparent background required to prevent white flash in dark mode, just using .appBackground doesn't work
+        webView.isOpaque = false
+        webView.backgroundColor = .clear
         if let content = itemContentHTML() {
             webView.loadHTMLString(content, baseURL: item.url)
         }