Add NativeOptions::window_builder for more customization (#3390)

* added a window builder hook for more customization

* `EFrame` -> `eframe`

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

crates/eframe/src/native/epi_integration.rs

@@ -75,7 +75,7 @@ pub fn read_window_info(
 pub fn window_builder<E>(
     event_loop: &EventLoopWindowTarget<E>,
     title: &str,
-    native_options: &epi::NativeOptions,
+    native_options: &mut epi::NativeOptions,
     window_settings: Option<WindowSettings>,
 ) -> winit::window::WindowBuilder {
     let epi::NativeOptions {
@@ -179,7 +179,10 @@ pub fn window_builder<E>(
         }
     }
 
-    window_builder
+    match std::mem::take(&mut native_options.window_builder) {
+        Some(hook) => hook(window_builder),
+        None => window_builder,
+    }
 }
 
 pub fn apply_native_options_to_window(