examples : add pydantic models to GBNF grammar generator (#4883)
* Create pydantic-models-to-grammar.py
* Added some comments for usage
* Refactored Grammar Generator
Added example and usage instruction.
* Update pydantic_models_to_grammar.py
* Update pydantic-models-to-grammar-examples.py
* Renamed module and imported it.
* Update pydantic-models-to-grammar.py
* Renamed file and fixed grammar generator issue.