eslint setup -- for all packages and without create-react-app

[gjoseph]

[copied from spenno#267]

When ditching CRA (#574 ) we lost the eslint configuration.

Unfortunately,

• the official react docs still recommends using eslint-config-react-app, which is part of CRA, which is unmaintained
• eslint-config-react-app depends on eslint 8 and doesn't seem to just-work with eslint 9
• the only alternative i could find is https://github.com/chiefmikey/eslint-config-react-app-bump, which didn't work for me (i can't recall why)
• the other alternative would be to configure all by hand, which, yuck

I've started setting this up at https://github.com/gjoseph/spenno/pull/805 But... I'd rather ditch cra entirely, and be able to move to eslint 9, for example.

[gjoseph]

This might also help setting eslint up for workspaces: https://gregory-gerard.dev/articles/eslint-in-a-monorepo