Add missing packaging dependency

I was using pynautobot and I noticed this packaging missing:
>>> nr = InitNornir(inventory={"plugin": "NautobotInventory","options": {"nautobot_url": "https://demo.nautobot.com/","nautobot_token": "a" * 40,},},)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/chadell/github.com/nornir-playground/example/.venv/lib/python3.10/site-packages/nornir/init_nornir.py", line 72, in InitNornir
    inventory=load_inventory(config),
  File "/Users/chadell/github.com/nornir-playground/example/.venv/lib/python3.10/site-packages/nornir/init_nornir.py", line 18, in load_inventory
    InventoryPluginRegister.auto_register()
  File "/Users/chadell/github.com/nornir-playground/example/.venv/lib/python3.10/site-packages/nornir/core/plugins/register.py", line 26, in auto_register
    self.register(entry_point.name, entry_point.load())
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/importlib/metadata/__init__.py", line 171, in load
    module = import_module(match.group('module'))
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/Users/chadell/github.com/nornir-playground/example/.venv/lib/python3.10/site-packages/nornir_nautobot/plugins/inventory/nautobot.py", line 20, in <module>
    import pynautobot
  File "/Users/chadell/github.com/nornir-playground/example/.venv/lib/python3.10/site-packages/pynautobot/__init__.py", line 7, in <module>
    from pynautobot.core.api import Api as api
  File "/Users/chadell/github.com/nornir-playground/example/.venv/lib/python3.10/site-packages/pynautobot/core/api.py", line 18, in <module>
    from packaging import version
ModuleNotFoundError: No module named 'packaging'
nautobot / pynautobot

Add missing packaging dependency #148
