Improve structure

[stancl]

Ideally this would be a proper npm project with a webpack build and it'd support both non-module <script src="..." init> usage as well as <script type="module"> usage.

I'd also like the codebase to be separated into a few files and ideally use a few TS interfaces, but that's not as important. I have an alternative version of this project that uses that TS structure, however I did not get the build working well, so I went with this simple implementation.

If anyone wants to contribute the improvements outlined above, I'd gladly pay something like a $50 reward.