Correctly type check annotation constructors.

[tim-evans]

Currently, our type checking around annotation constructors isn't strict enough and allows invalid construction of annotations.

What do you expect to happen?

Instantiating a new annotation should be a type error when the annotation requires attributes and the attributes are omitted from the output.

[tim-evans]

This post on the Artsy blog has a solution specifically for this:

constructor(
  attrs: {} extends Attributes
    ? { id?: string; start: number; end: number; attributes?: Attributes }
    : { id?: string; start: number; end: number; attributes: Attributes }
)

[tim-evans]

nb. I tried doing this and it requires us to use schemas 😭

The tldr on this is that TypeScript really doesn't like it when we have different arguments to annotation constructors, especially for the AnnotationConstructor class.