Improve JS packaging

[aaronshekey]

We need to include some source JS files to aid in importing from NPM.

Tasks:

• [ ] Correct exports field in package.json
• [ ] No bundled dependencies in exported js. You can ship multiple/unminified files if you like, I can bundle on my end as long as there's an import papertrail. Unminified is way easier to debug.
• [ ] Dependencies declared in package.json
• [ ] Correct types field in package.json
• [ ] Correct d.ts file

[abovedave]

Can we add a style link to the CSS in the package.json as well here?