Add Type Annotations

[jgmel]

We need to enhance our kea-python adding type annotations. This will improve code readability, maintainability, and help developers catch errors early.

Tasks:

• Create a kea.pyi file containing type annotations for all constants, classes, and methods in kea-python.
• Add a py.typed marker file to indicate the presence of type hints in the package.
• Update the setup.py.in file to include py.typed and kea.pyi in the package data.
• Verify the type annotations using a static type checker (e.g., mypy) to ensure there are no issues.

Benefits:

• Improved code quality and readability.
• Enhanced developer experience with better IDE support.
• Early error detection through static type checking.
• Easier maintenance and refactoring of the codebase.

Acceptance Criteria:

• Static type checks pass without errors.