Add colab/jupyter notebook in getting started page (#3885)

Summary: Pull Request resolved: #3885

Reviewed By: mcr229, cccclai

Differential Revision: D58262970

Author: mergennachin

docs/source/getting-started-setup.md

@@ -68,6 +68,11 @@ Note that the cross-compilable core runtime code supports a wider range of
 toolchains, down to C++11. See the [Runtime Overview](./runtime-overview.md) for
 portability details.
 
+## Quick Setup: Colab/Jupyter Notebook Prototype
+
+To utilize ExecuTorch to its fullest extent, please follow the setup instructions provided below. Alternatively, if you would like to experiment with ExecuTorch quickly and easily, we recommend using the following notebook [![for prototyping purposes](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/drive/1qpxrXC3YdJQzly3mRg-4ayYiOjC6rue3?usp=sharing).
+
+
 ## Environment Setup
 
 ### Create a Virtual Environment