Add support for official Python & Django versions

[irtazaakram]

Hi,

This PR

• adds support for Django 4.1 & 4.2
• drops support for Python 3.7 (EOL)
• drops support for Django 2.2, 3.0, 3.1 & 4.0 (EOL)

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

Thanks,

[alanjds]

This is great. I will just remove the 3.7 expectation on CI.

Thanks for your contribution @irtazaakram

[alanjds]

Also, please note that Travis is no longer the CI.

I kept the file during the "transition", but this is no longer being used now.