docs: Add quick_start.ipynb notebook equivalent of index.md Quickstart guide (#2128)

# What does this PR do?
- Adding a notebook equivalent of the
[getting_started/index.md#Quickstart
guide](https://github.com/meta-llama/llama-stack/blob/main/docs/source/getting_started/index.md).


## To discuss

**Note:** works locally, but I am encountering issues when attempting to
run through the notebook on Google Colab. Specifically, on the last step
to run the demo, the `knowledge_search` tool doesn't seem to be called
i.e.,:
```
rag_tool> Ingesting document: https://www.paulgraham.com/greatwork.html
prompt> How do you do great work?
inference> I don't have personal experiences or emotions, but I was trained on a large corpus of text data and use various techniques such as natural language processing (NLP) and machine learning algorithms to generate human-like responses.

```


I would expect to get something like:
```
rag_tool> Ingesting document: https://www.paulgraham.com/greatwork.html
prompt> How do you do great work?
inference> [knowledge_search(query="What is the key to doing great work")]
tool_execution> Tool:knowledge_search Args:{'query': 'What is the key to doing great work'}
tool_execution> Tool:knowledge_search Response:[TextContentItem(text='knowledge_search tool found 5 chunks:
....
....
```

docs/getting_started_llama4.ipynb

@@ -17,7 +17,9 @@
         "\n",
         "Read more about the project here: https://llama-stack.readthedocs.io/en/latest/index.html\n",
         "\n",
-        "In this guide, we will showcase how you can get started with using Llama 4 in Llama Stack.\n"
+        "In this guide, we will showcase how you can get started with using Llama 4 in Llama Stack.\n",
+        "\n",
+        "**💡 Quick Start Option:** If you want a simpler and faster way to test out Llama Stack, check out the [quick_start.ipynb](quick_start.ipynb) notebook instead. It provides a streamlined experience for getting up and running in just a few steps.\n"
       ]
     },
     {