Storybook config

### config.js ###
import { configure, addDecorator } from '@storybook/react';
import themeDecorator from './themeDecorator';

addDecorator(themeDecorator);

const loaderFn = () => {
  const req = require.context('../src/components', true, /\.stories\.js$/);
  req.keys().forEach(fname => req(fname));
};

configure(loaderFn, module);

### themeDecorator.js ###
import React from 'react';
import mainTheme from 'theme/mainTheme';
import { ThemeProvider } from 'styled-components';


const ThemeDecorator = storyFn => (
  <ThemeProvider theme={mainTheme}>{storyFn()}</ThemeProvider>
);

export default ThemeDecorator;

### main.js ###
module.exports = {
  stories: ['../src/**/*.stories.js'],
  addons: [
    '@storybook/preset-create-react-app',
    '@storybook/addon-actions',
    '@storybook/addon-links',
  ],
};