Re-eval lint rules for v6

We should gut all aesthetics-related lint rules and let `prettier` do the work for us. Something closer to what [we have in `spectacle-cli`](https://github.com/FormidableLabs/spectacle-cli/blob/master/.eslintrc), for example.

_[Originally posted by @ryan-roemer](https://github.com/FormidableLabs/spectacle/pull/786#discussion_r364358963)_