[python] added section "Generative AI" and tutorial for using LLaMA Guard

[tanya-rai]

Description

Created a new section in python for "Generative AI".
Added a tutorial (colab notebook) for using LLaMA Guard - an LLM-based input-output safeguard model.
(Plan to add more tutorials in the section for working with LLMs and generative AI image and audio models)

Motivation and Context

There are currently no tutorials linked for generative AI models. There's a ton of development happening now with LLMs and generative AI models - it would be nice to have tutorials linked in this awesome repo!

How Has This Been Tested?

Testing is all available in colab notebook that is attached.

Types of changes

No changes - just adding a tutorial :)

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have made checks to ensure URLs and other resources are valid