refactor: load signpost assets from cache

packages/pinball_components/lib/src/components/signpost.dart

@@ -88,12 +88,9 @@ class _SignpostSpriteComponent extends SpriteGroupComponent<SignpostSpriteState>
     final sprites = <SignpostSpriteState, Sprite>{};
     this.sprites = sprites;
     for (final spriteState in SignpostSpriteState.values) {
-      // TODO(allisonryan0002): Support caching
+      sprites[spriteState] = Sprite(
-      // https://github.com/VGVentures/pinball/pull/204
+        gameRef.images.fromCache(spriteState.path),
-      // sprites[spriteState] = Sprite(
+      );
-      //   gameRef.images.fromCache(spriteState.path),
-      // );
-      sprites[spriteState] = await gameRef.loadSprite(spriteState.path);
     }
 
     current = SignpostSpriteState.inactive;

packages/pinball_components/sandbox/lib/stories/flutter_forest/signpost_game.dart

@@ -17,8 +17,15 @@ class SignpostGame extends BasicBallGame with Traceable, TapDetector {
   Future<void> onLoad() async {
     await super.onLoad();
 
+    await images.loadAll([
+      Assets.images.signpost.inactive.keyName,
+      Assets.images.signpost.active1.keyName,
+      Assets.images.signpost.active2.keyName,
+      Assets.images.signpost.active3.keyName,
+    ]);
+
     camera.followVector2(Vector2.zero());
-    await add(Signpost()..priority = 1);
+    await add(Signpost());
     await traceAllBodies();
   }