Update workflows and readme

[skycode-src]

Thank you for this repository which seems very useful to me for any python development hence the need to keep it up to date.

This PR updates the versions of packages that were updated before but abandoned for 2 years... The objective being to make the workflow up to date with the current standard.

It upgrades:

• setup-python from v2 to v5, and
• checkout from v2 to v4.

Also added Django 4.2 and 5.0

The readme has been updated to reflect changes in the workflow.

[jefftriplett]

Thank you for the submission. I'm not sure the older versions are even useful at this point since Python 2.7 was dropped.

I might revisit it later than sooner.