* Bumped version of upstream [python-georss-client](https://github.com/exxamalte/python-georss-client) library to v0.17 that fixes a backwards compatibility issue with a fault in v0.16.
* Added Python 3.11 support.
* Added Python 3.12 support.
* Removed Python 3.7 support.
* Bumped library versions: black, flake8, isort.
* Migrated to pytest.
* Code quality improvements.