Hide egui-inspector window behind feature flag

The World Inspector widget shouldn't be enabled by default. This hides
it behind the "debug_ui" feature flag, along with the bevy_rapier2d
debug drawings.

The bevy_rapier2d debug plugin is now added when in debug mode, which
was not previously the case.

src/main.rs

@@ -1,11 +1,15 @@
 use bevy::{prelude::*, window::WindowResolution};
 
 use asteroids::{AsteroidPlugin, config::WINDOW_SIZE};
+
+#[cfg(feature = "debug_ui")]
 use bevy_inspector_egui::{bevy_egui::EguiPlugin, quick::WorldInspectorPlugin};
+#[cfg(feature = "debug_ui")]
+use bevy_rapier2d::render::RapierDebugRenderPlugin;
 
 fn main() {
-    App::new()
-        .add_plugins(DefaultPlugins.set(WindowPlugin {
+    let mut app = App::new();
+    app.add_plugins(DefaultPlugins.set(WindowPlugin {
         primary_window: Some(Window {
             canvas: Some("#game-canvas".to_owned()),
             resolution: WindowResolution::new(WINDOW_SIZE.0, WINDOW_SIZE.1),
@@ -13,8 +17,12 @@ fn main() {
         }),
         ..default()
     }))
-        .add_plugins(AsteroidPlugin)
-        .add_plugins(EguiPlugin::default())
+    .add_plugins(AsteroidPlugin);
+
+    #[cfg(feature = "debug_ui")]
+    app.add_plugins(EguiPlugin::default())
         .add_plugins(WorldInspectorPlugin::new())
-        .run();
+        .add_plugins(RapierDebugRenderPlugin::default());
+
+    app.run();
 }