Description:
    Creates a new generator at lib/generators. Pass the generator name
    under_scored.

Example:
    `fastapi-mvc generate generator my_controller`

    creates a project local my_controller generator:
        lib/generators/my_controller/
        lib/generators/my_controller/__init__.py
        lib/generators/my_controller/generator.py
        lib/generators/my_controller/template/USAGE
        lib/generators/my_controller/template/
