getConfig() {
    const plugins = this.getPluginConfig();
    const rules = this.getRuleConfig();

    this.__webpackConfig.plugins = plugins;
    const { module: mod } = this.__webpackConfig;
    if (!mod) {
      this.__webpackConfig.module = {
        rules,
      };
    } else {
      this.__webpackConfig.module.rules = rules;
    }
    return Object.assign({}, this.__webpackConfig);
  }
generate final config for webpack config
@return {Object}