I'm trying out a new editor setup, and it noticed that Prettier isn't
obviously installed! I think it makes sense to put it in dev deps, even
if there's not a direct hook calling it—though tbh maybe I should add it
to `yarn dev` somehow?
We add jsbuilding-rails to get esbuild running in the app, and then we copy-paste the files we need from impress-2020 into here!
I stopped at the point where it was building successfully, but it's not running correctly: it's not sure about `process.env` in `next`, and I think the right next step is to delete the NextJS deps altogether and use React Router instead.
