Update and add dependencies

[k3KAW8Pnf7mkmdSMPHz27]

1. Updates ESLint, Prettier, and Jest dependencies
2. Changes som ESLint rules
3. Fixes some ESLint complaints

[plocket]

Some good cleanup. I don't know enough about the environment to understand exactly what's going on with jest, though. You've added it to api/package.json, but removed it from api/setupTests.js.

I tried running yarn test in "api", but I got errors and couldn't run it, so I wasn't able to see more about what was going on there. That also meant I couldn't confirm that the updates to the various libraries didn't break anything, but other than jest it seems to be linting and such, so I'm not super concerned.

If you're sure all that is as it should be, the PR looks good to me. Let me know and I'll approve.

[k3KAW8Pnf7mkmdSMPHz27]

For now, this PR is superseded by experiments with xo-linter. We'll see which seems more suitable (dealing with eslint rules manually or going with xo-linter presets)