gha: not testing each supported python version

[ssbarnea]

Based on the package metadata, this library supports a long range of python versions but has no GHA pipelines testing them, which makes it a real risk for its consumers.

        'Programming Language :: Python :: 3',
        'Programming Language :: Python :: 3.5',
        'Programming Language :: Python :: 3.6',
        'Programming Language :: Python :: 3.7',
        'Programming Language :: Python :: 3.8',
        'Programming Language :: Python :: 3.9',
        'Programming Language :: Python :: 3.10',
        'Programming Language :: Python :: 3.11',