feat: added assets for drop rail

lib/game/game_assets.dart

@@ -12,6 +12,7 @@ extension PinballGameAssetsX on PinballGame {
       images.load(components.Assets.images.flipper.left.keyName),
       images.load(components.Assets.images.flipper.right.keyName),
       images.load(Assets.images.components.background.path),
+      images.load(Assets.images.components.spaceshipDropTube.path),
     ]);
   }
 }

lib/gen/assets.gen.dart

@@ -3,6 +3,8 @@
 ///  FlutterGen
 /// *****************************************************
 
+// ignore_for_file: directives_ordering,unnecessary_import
+
 import 'package:flutter/widgets.dart';
 
 class $AssetsImagesGen {
@@ -15,8 +17,13 @@ class $AssetsImagesGen {
 class $AssetsImagesComponentsGen {
   const $AssetsImagesComponentsGen();
 
+  /// File path: assets/images/components/background.png
   AssetGenImage get background =>
       const AssetGenImage('assets/images/components/background.png');
+
+  /// File path: assets/images/components/spaceship-drop-tube.png
+  AssetGenImage get spaceshipDropTube =>
+      const AssetGenImage('assets/images/components/spaceship-drop-tube.png');
 }
 
 class Assets {