es lib There is no css file in it

[busyzz]

this is src/index.js:

import React from 'react';
import './index.scss';

this is nwb.config.js:

module.exports = {
  type: 'react-component',
  npm: {
    esModules: true,
    umd: {
      global: 'ReactWxImageGrid',
      externals: {
        react: 'React',
      },
    },
  },
};

this is lib/index.js:

require('./index.scss');

Not found ./index.scss
This allowed me to introduce into the app causing an error，so how to solve this problem？