Add link for OD tutorial.

PiperOrigin-RevId: 501743340

Author: MarkDaoust

site/en/guide/_toc.yaml

@@ -104,13 +104,15 @@ toc:
   status: new
 - title: "Overview"
   path: /tfmodels
-- title: "Example: Image classification"
-  path: /tfmodels/vision/image_classification
 - title: "Training with Orbit"
   path: /tfmodels/orbit
 - title: "TFModels - NLP"
   path: /tfmodels/nlp
   status: external
+- title: "Example: Image classification"
+  path: /tfmodels/vision/image_classification
+- title: "Example: Object Detection"
+  path: /tfmodels/vision/object_detection
 
 - heading: "Estimators"
   status: deprecated