Implement ECS

I believe this is becoming more and more important.

Some interesting references from Hazel: [Components](https://github.com/TheCherno/Hazel/blob/master/Hazel/src/Hazel/Scene/Components.h), [Serialising](https://github.com/TheCherno/Hazel/blob/master/Hazel/src/Hazel/Scene/SceneSerializer.cpp).