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

Summary:
Pull Request resolved: #3885

bypass-github-export-checks
bypass-github-pytorch-ci-checks
bypass-github-executorch-ci-checks

Reviewed By: mcr229, cccclai

Differential Revision: D58262970

Author: mergennachin

docs/source/getting-started-setup.md

@@ -68,6 +68,12 @@ 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 [colab notebook](https://colab.research.google.com/drive/1qpxrXC3YdJQzly3mRg-4ayYiOjC6rue3?usp=sharing) for prototyping purposes.
+
+
+
 ## Environment Setup
 
 ### Create a Virtual Environment