Knx-ga-exporter

Features
- Support configuration via JSON (based on [jsonargparse](https://jsonargparse.readthedocs.io/))

Infrastructure
- Rework to [hyper-modern structure](https://cjolowicz.github.io/posts/hypermodern-python-01-setup/) with [python-pdm](https://pdm-project.org/)
- Implement tests (100% coverage)
- Publish to [PyPI](https://pypi.org/) index

Dependencies
- Bump openpyxl to 3.1.5

Fixes & Improvements

- Detect missing group address (GA).
- Handling of encoding errors.
- Improved log output formatting.

Initial Release