Publish TypeScript Types #213

To use TypeScript types with this module (in a different package), we need to publish types:

This is done pretty simply, by adding the "types" property in our package.json and ensure we build the types before publishing:

• Docs: https://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html
• 30 sec guide: https://medium.com/cameron-nokes/the-30-second-guide-to-publishing-a-typescript-package-to-npm-89d93ff7bccd