Mordernize the Python library

[eoyilmaz]

The library file structure is showing its age. We need to update it.

• Move everything in timecode to src/timecode
• Remove setup.cfg and setup.py or simplify setup.py to just a single call to from setuptools import setup.
• Add pyproject.toml.
• Add ruff support and format the library and make it sure that it passes all linting errors.
• Add a VERSION file and update pyproject.toml to parse it for the library version.
• Add Python 13 and 14 support.
• Add a Makefile for common targets like: build, test, new-release, clean and clean-all