Fix some enemy stuff

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

lib/features/entities/entity.dart

@@ -21,5 +21,10 @@ abstract class Entity<T> {
     this.lastActionTime = 0,
   });
 
+  set position(Coordinate2D pos) {
+    x = pos.x;
+    y = pos.y;
+  }
+
   Coordinate2D get position => Coordinate2D(x, y);
 }