nb/rag_chatbot: added references in the first cell

notebooks/rag_chatbot.ipynb

@@ -13,7 +13,9 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "In this notebook I will demonstrate how to build the backend of a RAG-application, that will allow users to interact with uploaded pdf documents and provided URL's. What's special here is that it's entirely free, and works well, at least for limited traffic required for experimenting."
+    "In this notebook I will demonstrate how to build the backend of a RAG-application, that will allow users to interact with uploaded pdf documents and provided URL's. What's special here is that the resulting solution is entirely free (subject to HuggingFace inference API rate limits).\n",
+    "\n",
+    "Note: the code snippets below have been copied and simplified from my original code [here](https://github.com/OnurKerimoglu/chat_with_docs/blob/main/src/rag.py), which is in turn deployed to HuggingFace space [here](https://huggingface.co/spaces/OnurKerimoglu/rag_chat), which may well be sleeping due to inactivity (don't hesitate to wake it up!)"
    ]
   },
   {