Add support for eslint-plugin-jest

[wesleycho]

For typical development while using create-react-app, inevitability there will be a time when developers accidentally commit stuff like fit or fdescribe - I would like CRA to have built in support for eslint-plugin-jest and set those as warnings so they can be caught as hard errors in CI.

[mrmckeb]

Hi @wesleycho, you can already add this by extending our ESLint config.

For example, in your package.json:

{ 
  "eslintConfig": {
    "extends": ["react-app"],
    "plugins": [],
    "rules": {}
  }
}

Right now, these will be used by your editor, but won't break builds.

My team use lint-staged with husky to run a pre-commit hook that performs a command, and if it fails, the commit won't happen. You can see more on that here: https://facebook.github.io/create-react-app/docs/setting-up-your-editor#formatting-code-automatically

We generally only do linting on prepush and on the CI though...

Let me know if this helps!