Add `packaging` to dependencies

No module named 'packaging
[f006rq8@x01 reproman]$ reproman --version
Traceback (most recent call last):
  File "/dartfs-hpc/rc/home/8/f006rq8/conda/bin/reproman", line 8, in <module>
    sys.exit(main())
  File "/dartfs-hpc/rc/home/8/f006rq8/conda/lib/python3.10/site-packages/reproman/cmdline/main.py", line 222, in main
    parser = setup_parser()
  File "/dartfs-hpc/rc/home/8/f006rq8/conda/lib/python3.10/site-packages/reproman/cmdline/main.py", line 135, in setup_parser
    _mod = import_module(_intfspec[0], package='reproman')
  File "/dartfs-hpc/rc/home/8/f006rq8/conda/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 "/dartfs-hpc/rc/home/8/f006rq8/conda/lib/python3.10/site-packages/reproman/interface/diff.py", line 21, in <module>
    from ..distributions.conda import CondaDistribution
  File "/dartfs-hpc/rc/home/8/f006rq8/conda/lib/python3.10/site-packages/reproman/distributions/conda.py", line 12, in <module>
    from packaging.version import Version
ModuleNotFoundError: No module named 'packaging'
ReproNim / reproman

Add `packaging` to dependencies #608
