code: function getWebpackConfig(userWebpackConfigOpt, wpAffectingOpts) {
  
  	let extend = (data) => { return data }
  	if (userWebpackConfigOpt) {
  		const userWebpackConfigPath = path.resolve(process.cwd(), userWebpackConfigOpt);
  		const userWebpackConfigFunc = require(userWebpackConfigPath);
  		extend = userWebpackConfigFunc.default;
  	}
  
  	const baseConfig = require(path.join(__dirname, "webpack/webpack4.config.fn.js")).default(wpAffectingOpts);
  	return extend(baseConfig);
  }
docs: get the webpack configuration object loads data from default configuration at webpack/webpack4.config.fn.js, and extends it by calling user-supplied function, if one was provided