Update fonts.mdx

Author: mintlify[bot]

fonts.mdx

@@ -98,6 +98,21 @@ You can configure separate local fonts for headings and body text:
 }
 ```
 
+### External font URLs
+
+You can also use external font URLs instead of local files:
+
+```json docs.json
+{
+  "fonts": {
+    "family": "Hubot Sans",
+    "source": "https://mintlify-assets.b-cdn.net/fonts/Hubot-Sans.woff2",
+    "format": "woff2",
+    "weight": 400
+  }
+}
+```
+
 ## Font configuration reference
 
 <ResponseField name="fonts" type="object">