Decouple the engine from Flutter entirely

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

packages/wolf_3d_data/lib/src/io/engine_input.dart

@@ -0,0 +1,11 @@
+import 'package:wolf_3d_entities/wolf_3d_entities.dart';
+
+class EngineInput {
+  bool isMovingForward = false;
+  bool isMovingBackward = false;
+  bool isTurningLeft = false;
+  bool isTurningRight = false;
+  bool isInteracting = false;
+  bool isFiring = false;
+  WeaponType? requestedWeapon;
+}