Add credits to the model authentication notebook

Author: besirkurtulmus

model_authentication/model_authentication.ipynb

@@ -269,6 +269,15 @@
     "\n",
     "You can call this API endpoint from anywhere: your mobile app, your website, and more..."
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Credits\n",
+    "\n",
+    "The Tensorflow example was copied from an official Tensorflow Google Colab notebook that can be found [here](https://colab.research.google.com/github/tensorflow/docs/blob/master/site/en/tutorials/quickstart/beginner.ipynb)."
+   ]
   }
  ],
  "metadata": {