Various upgrades (Python version, dependencies, Poetry, pre-commit, and more)

[john-sandall]

• Various upgrades (#40)
• Behind-the-scenes
  • Upgrade Python to 3.9.13
  • Upgrade all dependencies to latest with NumPy/pandas/Matplotlib/scikit-learn matching CoCalc versions.
  • Switch from pip-tools to Poetry (configuration in pyproject.toml)
  • Update Development Setup guidance in README.md
  • Integrate & configure flake8, pylint, black & other linters.
  • Added pre-commit configuration.
  • Updated VS Code settings.json
  • Added linestripper.py to keep EOF newlines out of solutions code (better attendee UX) yet black-compliant.
  • Added CHANGELOG.md and started versioning releases.
• Workshop materials
  • Reviewed all workshop materials for deprecations.
  • Replaced all single quotes in solutions with double quotes for black compliance.
  • Added EOF newlines to datasets.
  • Other minor changes: trailing whitespace, trailing commas, isort compliant solution code.