Add support for official Python & Django versions

[irtazaakram]

Hi @daisylb,

This PR

• adds support for Python 3.9, 3.10, 3.11 & 3.12
• adds support for Django 3.2 & 4.2 (LTS)
• update GitHub actions
• drops support for Python 3.5, 3.6, & 3.7 (EOL)
• drops support for Django 2.2 & 3.0 (EOL)

Please can we have a new release after this PR is merged.

Thanks,