Update guides_master.py (#2164)

Author: divyashreepathihalli

scripts/guides_master.py

@@ -115,6 +115,10 @@
             "path": "migrating_to_keras_3",
             "title": "Migrating Keras 2 code to Keras 3",
         },
+        {
+            "path": "keras_nnx_guide",
+            "title": "How to use Keras with NNX backend",
+        },
         # {
         #     "path": "preprocessing_layers",
         #     "title": "Working with preprocessing layers",