clarify you can make noindex a global specification (#449)

* clarify you can make noindex a global specification

* Update settings/seo.mdx

---------

Co-authored-by: Ricardo Nunez <[email protected]>

Author: dino475

settings/seo.mdx

@@ -70,4 +70,12 @@ If you want to stop a page from being indexed by search engines, you can include
 ---
 noindex: true
 ---
+```
+
+You can also specify `noindex` for all pages in your docs by setting the `metadata.robots` field to `"noindex"` in your `mint.json`:
+
+```json
+"metadata": {
+   "robots": "noindex"
+}
 ```