BREAKING CHANGE: It's no longer allowed to omit the '-loader' suffix when using loaders.

BREAKING CHANGE: It’s no longer allowed to omit the ‘-loader’ suffix when using loaders.
You need to specify ‘css-loader’ instead of ‘css’,
原因：webpack新版本不支持缩写，将提示的webpack.config.js位置改成全写

    {
        test: /\.less$/,
        loader: 'style-loader!css-loader!less-loader'
      }