I want a simple ECS system for my meshes, lighting, and camera

## Scenes and Nodes
- Scene is the basis for a game level/world
- Structure of the scene is tree-like, where the Scene is the root
- Nodes are nodes in the scene tree
- Nodes have to propagate:
- Transformation (hierarchical transformation)
- Input events
- Frame event
- We can have as many nodes nested in a node and as deep as we want
- Nodes have their own properties, some of which can be seen and edited in the editor

## Custom nodes
- User can create custom nodes from pre-built nodes
- Custom nodes can be used similarly to built-in nodes

## Serialization
- Each scene can be serialized containing information of all nodes in it
- Custom node can be saved to disk, but its information in the scene will be stored in the saved scene