servoshell: Migrate to egui-file-dialog from tinyfiledialogs (#34823)

This is the first step toward completely replacing tinyfiledialogs with
an egui-based solution.

Signed-off-by: L Ashwin B <lashwinib@gmail.com>

ports/servoshell/desktop/minibrowser.rs

@@ -391,6 +391,10 @@ impl Minibrowser {
                 return;
             };
 
+            egui::CentralPanel::default().show(ctx, |_| {
+                webview.update(ctx);
+            });
+
             CentralPanel::default()
                 .frame(Frame::none())
                 .show(ctx, |ui| {