add `packaging` to setup.py file?

[michaelbabyn]

After installing plotly==5.13.1, import plotly.io failed with the below error due to packaging not being installed in my python 3.6 env by default:

      import plotly.io as pio
    File "/app/.heroku/python/lib/python3.6/site-packages/plotly/__init__.py", line 35, in <module>
      from plotly import (
    File "/app/.heroku/python/lib/python3.6/site-packages/plotly/io/__init__.py", line 12, in <module>
      from ._renderers import renderers, show
    File "/app/.heroku/python/lib/python3.6/site-packages/plotly/io/_renderers.py", line 7, in <module>
      from packaging.version import Version
ModuleNotFoundError: No module named 'packaging'```

[mgorny]

I can confirm.

[nicolaskruchten]

Ah, this is unfortunate, sorry about this, we'll fix this in the next patch in a day or two.

[mgorny]

Thank you!