Wagtail 7.1 updates

[damwaingames]

The changes primarily focus on updating the supported versions of Python, Django, and Wagtail, and removing support for older versions.

Superceeds PR #57, #59 and #60.

Updates to testing environment and compatibility:

• tox.ini:
  • Removed Wagtail 5.2, 6.1, 6.2 (EOL) and Django 5.0 (EOL) from the environment list.
  • Added support for Wagtail 6.3, 7.0 and 7.1, Django 5.2 and Python 3.12.
• setup.py:
  • Removed Django 5.0 and Wagtail 5 from the classifiers and added Wagtail 7, Django 5.2 and Python 3.13 da0cc91.
  • Updated required version of Wagtail from 5.2 to 6.3 9c517fc.

Documentation updates:

• CHANGELOG.md: Added an entry for the unreleased changes.

Other updates:

• Fix tests failing due to django-tasks 1b98aff