We currently do the same thing Jest does: no hooks, but we offer it as `npm run prettier`, and we also run the comparison on CI (so if the prettier output is di

We currently do the same thing Jest does: no hooks, but we offer it as `npm run prettier`, and we also run the comparison on CI (so if the prettier output is different, the PR fails). This means the code is always checked in formatted, but people need to remember to run `npm run prettier` or CI will fail.