在react中使用sass时，引入.scss文件失效
尝试很多方法没法解决，最终找到解决方法，希望能帮助正在坑里挣扎的筒子~

在node_modules文件夹下，找到react-scripts ==> config文件夹， 在该配置文件夹下找到 webpack.config.dev.js和webpack.config.prod.js。
在file-loader之前添加style-loader, css-loader, sass-loader
代码如下：

          {
            test: /\.scss$/,
            loaders: ['style-loader', 'css-loader', 'sass-loader'],
          },
          // "file" loader makes sure those assets get served by WebpackDevServer.
          // When you `import` an asset, you get its (virtual) filename.
          // In production, they would get copied to the `build` folder.
          // This loader doesn't use a "test" so it will catch all modules
          // that fall through the other loaders.
          {
            // Exclude `js` files to keep "css" loader working as it injects
            // its runtime that would otherwise processed through "file" loader.
            // Also exclude `html` and `json` extensions so they get processed
            // by webpacks internal loaders.
            exclude: [/\.(js|jsx|mjs)$/, /\.html$/, /\.json$/],
            loader: require.resolve('file-loader'),
            options: {
              name: 'static/media/[name].[hash:8].[ext]',
            },
          }