Add "packaging" to requirements.txt

[kylefmohr]

I ran these instructions from the README:

 git clone https://github.com/stanislav-web/OpenDoor.git
 cd OpenDoor/
 pip3 install -r requirements.txt
 chmod +x opendoor.py

Then when I ran python3 opendoor.py, I received the following error message

Traceback (most recent call last):
  File "/Users/<user>/OpenDoor/opendoor.py", line 31, in <module>
    from src import Controller, SrcError
  File "/Users/<user>/OpenDoor/src/__init__.py", line 21, in <module>
    from .controller import Controller
  File "/Users/<user>/OpenDoor/src/controller.py", line 19, in <module>
    from src.core.decorators import execution_time
  File "/Users/<user>/OpenDoor/src/core/__init__.py", line 29, in <module>
    from .helper import Helper as helper
  File "/Users/<user>/OpenDoor/src/core/helper/__init__.py", line 19, in <module>
    from .helper import Helper
  File "/Users/<user>/OpenDoor/src/core/helper/helper.py", line 25, in <module>
    from packaging import version
ModuleNotFoundError: No module named 'packaging'

Running pip3 install packaging fixed this issue, now python3 opendoor.py returns the help docs as expected.

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This change is 

[stanislav-web]

@kylefmohr Thank you much