Support Django v4.2, v5.x and v6.x

[sevdog]

Django 4.2 has been released, just the day before this library released its version 2.0.0 (see #23).

Since it does not have any particular breaking changes which may involves this library it should be easy to support it just by adding the value to tox configurations.

So technically this is just a "add tests for Django 4.2" request.

---

PS: in the meantime I want to highlight that this package is still marked to support Django 1.10, even if it is no more configured in tox

django-relativedelta/setup.py

Line 58 in a62261c

'Django >= 1.10',

PPS: Also, setup metadata does not declare to support Django 2.x nor Python3.8 which are in tox configuration and are currently tested.

django-relativedelta/setup.py

Lines 41 to 50 in a62261c

	'Framework :: Django :: 3.2',
	'Framework :: Django :: 4.0',
	'Framework :: Django :: 4.1',
	'Intended Audience :: Developers',
	'License :: OSI Approved :: MIT License',
	'Operating System :: OS Independent',
	'Programming Language :: Python',
	'Programming Language :: Python :: 3',
	'Programming Language :: Python :: 3.9',
	'Programming Language :: Python :: 3.10',

[Mapiarz]

Bump with support for 5.0 ;)

[sevdog]

Django 5.2 is behind the corner and there are still no tests against versions 4.2, 5.0 and 5.1, nor there are tests against any recent python version (>3.10). When these tests will be performed?

[sevdog]

Django 6.1 has been released, it will be good having it in test matrix.