Added a basic usage section showing the help block of the cli utiltiy.

[Utkarsh-vishnoi]

Enhanced README.md with detailed usage instructions for the exo command-line tool, including command options, examples for running models, and API interaction using curl. This update improves clarity and usability for users.

[AlexCheema]

It's a little verbose and overlaps with other parts of the readme (e.g. the curl example is already in there).

Maybe we can put this below the examples in the README and remove the redundant stuff.