add eslint + small formatting changes

[techniq]

I'd prefer to format with prettier if that's OK (I know the formatting needs cleaned up though).

[techniq]

I've not looked into it too much, but would it be worthwhile to extend prettier/react as well - https://github.com/prettier/eslint-config-prettier. I'm not exactly sure what it does, but I've seen other configs reference it (I think to keep eslint/prettier from interferring more). I've only used eslint or prettier in isolation TBA.

[techniq]

Thanks!