Fix IME input handling (#20)

bevy_winit does not call `set_ime_allowed()` during initial window
creation when `Window::ime_enabled` is `true`. The `changed_windows`
system only fires when the value differs from cache, but the cache
is initialized from the window itself so they start equal. Since
winit 0.27+ requires explicit `set_ime_allowed(true)`, no Ime events
were ever generated.

examples/simple.rs

@@ -5,7 +5,16 @@ use bevy_cef::prelude::*;
 
 fn main() {
     App::new()
-        .add_plugins((DefaultPlugins, CefPlugin::default()))
+        .add_plugins((
+            DefaultPlugins.set(WindowPlugin {
+                primary_window: Some(Window {
+                    ime_enabled: true,
+                    ..default()
+                }),
+                ..default()
+            }),
+            CefPlugin::default(),
+        ))
         .add_systems(
             Startup,
             (spawn_camera, spawn_directional_light, spawn_webview),