Automatically generate screenshots for all examples (#2379)

examples/file_dialog/src/main.rs

@@ -5,6 +5,7 @@ use eframe::egui;
 fn main() {
     let options = eframe::NativeOptions {
         drag_and_drop_support: true,
+        initial_window_size: Some(egui::vec2(320.0, 240.0)),
         ..Default::default()
     };
     eframe::run_native(