Wagtail 72 maintenance and Testing Improvements

[nickmoreton]

This pull request introduces a number of significant updates to the project, primarily focused on modernizing dependencies, improving documentation, and adding a complete test application for development and manual testing.

Dependency and Compatibility Updates:

• Dropped support for Wagtail versions below 7.0 and Python versions below 3.10, requiring Wagtail >=7.0 and Python >=3.10. Legacy import conditionals for older Wagtail versions have been removed.
• Migrated packaging configuration from setup.py to pyproject.toml

Documentation Improvements:

• Updated the README.md to clarify new requirements (Python 3.10+, Wagtail 7.0+) and add a new section with detailed instructions for setting up a development environment and running the test app.