eslint config should enable "react/jsx-key"

[mdj-uk]

The eslint config from this repo is officially recommended in the react docs.

I'm surprised that various rules from eslint-plugin-react recommended config are not enabled here.

For example, react/jsx-key is important for a) decreasing the risk of bugs and b) getting rid of noise in console logs (which can swamp more important errors/warnings).

I'm wondering if there's a good reason for this?

If not, would be happy to submit a PR.