Added "readonly" modifier to classes in "constants" package
Code reformat
Making Gameplay's public fields private, adding [SerializeField] and get-methods for them
Making HealthBarForEnemy's public field private and adding [SerializeField]
Making TowerSlot's public fields private, adding [SerializeField] and get-methods for them
Making public fields private, adding [SerializeField] and get-methods for factories
Added TowerSlot state diagram
Added CoordinateConverterTest image
Added list of requirements