Support PHP 8.4 / WP 7.0

[kadamwhite]

This should be updated to add a dockerfile for PHP 8.4, and to permit usage of WordPress versions up through 7.0.

This will involve updating the arrays in .github/workflows/image.yml to include PHP 8.4, and WP 6.9 / 7.0; it will also require a new Dockerfile for PHP 8.4.