fix: Update authoring.mdx

Author: abernier

docs/getting-started/authoring.mdx

@@ -355,7 +355,7 @@ Instead of `files`, a `folder` prop allow you to pass a folder containing all th
 
 `folder` path is relative to the `.mdx` file:
 
-```
+```text
 |-- getting-started
 |   |-- authoring.mdx             <= relative to this article
 |   `-- authoring-sandpack-cloud  <= the folder