Adding tutorial content for "Train a Large Language Model (LLM) using TPUs on GKE with JAX"

[pulasthi]

Propose to adding content (Scripts and training code files) for the tutorial Train a Large Language Model (LLM) using TPUs on GKE with JAX,

The changes have been validated and tested on GKE for both standard and autopilot clusters.

CL for the current draft tutorial: https://critique.corp.google.com/cl/855858604

[NimJay]

Thank you for creating an issue. Please move forward with the pull-request.