Add type annotations to the python codebase

[youtux]

🤔 What's changed?

• Added type annotations to the python codebase.
• Added py.typed file marker

There are still quite some errors (actual bug, mypy idiosyncrasies, ...) , but at least all the signatures are annotated.

⚡️ What's your motivation?

Static type checking make things safer and easier to find usages.

🏷️ What kind of change is this?

• 🏦 Refactoring/debt/DX (improvement to code design, tooling, etc. without changing behaviour)

♻️ Anything particular you want feedback on?

📋 Checklist:

• I agree to respect and uphold the Cucumber Community Code of Conduct
• I've changed the behaviour of the code
  • I have added/updated tests to cover my changes.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• Users should know about my change
  • I have added an entry to the "Unreleased" section of the CHANGELOG, linking to this pull request.

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[jsa34]

Perhaps instead of using typing.List instead of list for the typings, given I guess that we are so close to EOL for py3.8, should we just go for 3.9+?

[youtux]

Perhaps instead of using typing.List instead of list for the typings, given I guess that we are so close to EOL for py3.8, should we just go for 3.9+?

I fixed those lines, it was no big deal, so let's keep 3.8 until it goes EOL

[jsa34]

Just my initial spots

[jsa34]

Looks good to me.