fix 加载多个loader 应该使用use (#1654)

Co-authored-by: 小陈啊！！！ <chen.lingang@qq.com>

Author: xiaochena

src/content/loaders/less-loader.mdx

@@ -44,7 +44,7 @@ module.exports = {
     rules: [
       {
         test: /\.less$/i,
-        loader: [
+        use: [
           // compiles Less to CSS
           'style-loader',
           'css-loader',