config-overrides.js

const rewireMobX = require('react-app-rewire-mobx');
const { injectBabelPlugin } = require("react-app-rewired");

/* config-overrides.js */
module.exports = function override(config, env) {
  config = rewireMobX(config,env);
  config = injectBabelPlugin("babel-plugin-styled-components", config);
  return config;
}