Create parameters package and define velocity parameter

ros2_ws/src/python_parameters/LICENSE

ros2_ws/src/python_parameters/package.xml

ros2_ws/src/python_parameters/python_parameters/__init__.py

...python_parameters/python_parameters/velocity_parameter.py

ros2_ws/src/python_parameters/resource/python_parameters

ros2_ws/src/python_parameters/setup.cfg

ros2_ws/src/python_parameters/setup.py

ros2_ws/src/python_parameters/test/test_copyright.py

ros2_ws/src/python_parameters/test/test_flake8.py

ros2_ws/src/python_parameters/test/test_pep257.py