ESLint setup for Jest

[IlCallo]

Same as #95 but for Jest, we should rely on https://github.com/jest-community/eslint-plugin-jest.
.eslintrc.js file should be added automatically inside test/jest folder upon initialization.

Suggested ESLint configuration:

module.exports = {
  extends: [
    // Removes 'no-undef' lint errors for Jest global functions (`describe`, `it`, etc),
    //  add Jest-specific lint rules and Jest plugin
    // See https://github.com/jest-community/eslint-plugin-jest#recommended
    'plugin:jest/recommended',
    // Uncomment following line to apply style rules
    // 'plugin:jest/style',
  ],
};