add ambient audio track

src/main.rs

@@ -145,6 +145,15 @@ fn music(asset_server: Res<AssetServer>, mut commands: Commands) {
             ..default()
         },
     ));
+
+    commands.spawn((
+        AudioPlayer::new(asset_server.load("sfx/ambient/downtown.ogg")),
+        PlaybackSettings {
+            mode: PlaybackMode::Loop,
+            volume: Volume::new(1.),
+            ..default()
+        },
+    ));
 }
 
 fn write_trenchbroom_config(server: Res<TrenchBroomServer>) {