Break out spawnable entities and use a registry to spawn them.

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

lib/features/entities/entity.dart

@@ -0,0 +1,21 @@
+enum EntityState { staticObj, idle, patrolling, shooting, pain, dead }
+
+abstract class Entity<T> {
+  double x;
+  double y;
+  int spriteIndex;
+  double angle;
+  EntityState state;
+  int mapId;
+  int lastActionTime;
+
+  Entity({
+    required this.x,
+    required this.y,
+    required this.spriteIndex,
+    this.angle = 0.0,
+    this.state = EntityState.staticObj,
+    this.mapId = 0,
+    this.lastActionTime = 0,
+  });
+}