config-overrides.js

const { injectBabelPlugin } = require('react-app-rewired');
const rewireLess = require('react-app-rewire-less');
const rewireMobX = require('react-app-rewire-mobx');

module.exports = function override(config, env) {
  config = injectBabelPlugin(
    ['import', { libraryName: 'antd', libraryDirectory: 'es', style: true }], // change importing css to less
    config
  );
  config = rewireLess.withLoaderOptions({
    // modifyVars: { "@primary-color": "#1DA57A" },
    javascriptEnabled: true,
  })(config, env);
  config = rewireMobX(config, env);
  return config;
};