fix: introduce the packaging dependency

[WilliamBergamin]

Summary

This PR aims to resolve #29 where the packaging dependency is not installed on the system.

It seems like pip which uses the packaging project duplicates the logic into its source code rather then installing it as a dependency. Seems like the chicken and egg problem 🥚

This PR aims to introduce packaging as a dependency to the project, alternatively we could duplicate the logic like pip does, or find another solution rather then adding our first "real" dependency

Testing

1. Create a new project with slack create -t https://github.com/slack-samples/bolt-python-custom-function-template
2. edit the requirements.txt file so that it only contains (many other packages have the packaging dependency)

slack-cli-hooks
slack-bolt==1.19.0rc1

3. run slack update
4. Everything should work 🟢

Special notes

Important to not that many python development tools like pip, black and pytest use the packaging project, this is why we did not catch this error sooner

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run ./scripts/install_and_run_tests.sh after making the changes.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.58%. Comparing base (2d7cc13) to head (5aecbd6).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #39   +/-   ##
=======================================
  Coverage   94.58%   94.58%           
=======================================
  Files          11       11           
  Lines         203      203           
=======================================
  Hits          192      192           
  Misses         11       11           

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[zimeg]

🐣 Awesome! The slack update is working wonderfully for me now!

[seratch]

I see! LGTM