Add Entity and Id extension code generator

[BeanCheeseBurrito]

There should be a code generator that generates wrappers around the Entity and Id structs for objects that inherit from them. It would make the following code a bit nicer to write.

• Old

  
  world.Component<Position>()
  .Ctor(...)
  .Dtor(...);

// Entity builder functions need to be accessed through Component.Entity world.Component().Entity .Add(...) .Add(...);

- **New**
```cs
// Both component and entity functions should be accessible from the component struct
world.Component<Position>()
    .Ctor(...)
    .Dtor(...)
    .Add(...)
    .Add(...);