Migrate to TypeScript

[SchaeStewart]

The project has grown in size and scope and given the ephemeral nature of a volunteer project, I think additional type safety will yield a lot of benefits.

To start we should add types to the backend, and update the build/deploy/run process to work with TypeScript.

I'm open to other opinions or reasons we shouldn't migrate, I'm also open to migrating the UI, but I think the backend will be a better place to start.