tox.ini: Add Python 3.12 and Django 5.0

[cclauss]

Related to #167

• starting prepare to bump new version for Django 4.2.X support #167

https://pypi.org/project/Django

https://www.djangoproject.com/weblog/2023/dec/04/django-50-released

Django 4.1 has reached the end of extended support. The final security release (4.1.13) was issued on November 1st. All Django 4.1 users are encouraged to upgrade to Django 4.2 or later.

https://docs.djangoproject.com/en/5.0/releases/5.0

Django 5.0 supports Python 3.10, 3.11, and 3.12.

https://docs.djangoproject.com/en/5.0/faq/install/#what-python-version-can-i-use-with-django