[PICOTRON] Improve README for readability

[paragao]

The README.md on the picotron test case (3.test_cases/pytorch/picotron) lacks basic instructions. It assumes users are familiar with the process and already have the HF CLI installed.

ACTION:

• add instructions on how to get the HF CLI
• explain what the ./create_config.py does
• rewrite the README assuming users are not familiar with the process

[github-actions]

This issue is stale because it has been open for 30 days with no activity.