Support Django 4

[EwoutH]

Django 4.0 was released earlier this month! It would be awesome if Django Chartjs was updated to support it.

[iragm]

What needs to be changed? I am using Django 5.0.3 with the current release of django-chartjs and it seems to work fine.

[Natim]

@iragm we can update https://github.com/peopledoc/django-chartjs/blob/master/setup.py#L28