Custom Angular library converts const to declared interface on build

Question

I'm creating a library of angular components using ng-packagr. I have a set of static data I want included so my apps have access to same set of data. I have a this, as an example, in a bookList.ts file:

export const bookList = {
  CAT: { title: 'Cat Book' },
  DOG: { title: 'Dog Book' },
  BIRD: { title: 'Bird Book' }
}

When I run ng build it's output as

export declare const bookList = {
      CAT: { title: string },
      DOG: { title: string },
      BIRD: { title: string }
    }

How can I include the data in my package and avoid the conversion?