chore: added mobile dialog content test

test/start_game/widgets/how_to_play_dialog_test.dart

@@ -1,5 +1,6 @@
 // ignore_for_file: prefer_const_constructors
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:pinball/l10n/l10n.dart';
@@ -15,12 +16,24 @@ void main() {
       l10n = await AppLocalizations.delegate.load(Locale('en'));
     });
 
-    testWidgets('displays content', (tester) async {
+    testWidgets('displays content for desktop', (tester) async {
+      debugDefaultTargetPlatformOverride = TargetPlatform.macOS;
       await tester.pumpApp(HowToPlayDialog());
       expect(find.text(l10n.howToPlay), findsOneWidget);
       expect(find.text(l10n.tipsForFlips), findsOneWidget);
       expect(find.text(l10n.launchControls), findsOneWidget);
       expect(find.text(l10n.flipperControls), findsOneWidget);
+      debugDefaultTargetPlatformOverride = null;
+    });
+
+    testWidgets('displays content for mobile', (tester) async {
+      debugDefaultTargetPlatformOverride = TargetPlatform.iOS;
+      await tester.pumpApp(HowToPlayDialog());
+      expect(find.text(l10n.howToPlay), findsOneWidget);
+      expect(find.text(l10n.tipsForFlips), findsOneWidget);
+      expect(find.text(l10n.tapAndHold), findsOneWidget);
+      expect(find.text(l10n.tapLeftRightScreen), findsOneWidget);
+      debugDefaultTargetPlatformOverride = null;
     });
   });