Consider some node tooling

[slifty]

Oh node, how we love thee.

In my work on #11 I'm moving the project to type: "module" which lets us do things like export foo() in a utility file.

Since it never hurts to move into modern node, I'd like to propose we consider:

1. Adding babel
2. Adding eslint (we have eslint in the project, though it is not clear when or how to run it
3. Adding tests (I'm most familiar with jest)

Once we do this we can consider adding some CI to invoke the linter + tests before allowing a PR to merge. This will all be especially useful as we consider #18

[slifty]

Adding Babel will also make the eventual move to TypeScript easier 😈