recommended shared config

[benmosher]

Seems to be a common pattern amongst plugins.

Probably should be a combo of errors and warnings?

Also: see #416, probably want the following parser options, too:

  parserOptions: {
    sourceType: 'module',
    ecmaVersion: 6,
    ecmaFeatures: { experimentalObjectRestSpread: true, jsx: true },
  },

@jfmengels this is probably another way to steer users towards static analysis. I have felt like the errors and warnings shared configs were not named clearly, anyway. Probably will keep them since it doesn't hurt, but merge them (or maybe just take errors) for the recommended version.

[benmosher]

@jfmengels would love your feedback on what I put together for this

[jfmengels]

I left some comments in the commit. I'd be happy to discuss it more if you want to. Either in a new issue or in the commit.