Centralize and consolidate PHP github pipelines using required workflows

[arzola]

Currently we have one Github step that usually runs in all of our PHP repositories

https://github.com/pressbooks/pressbooks/blob/dev/.github/workflows/standards-and-tests.yml

This uses a bash script to install and run WP for testing purposes, it also create a WP package using wp package to pack and build the plugin ready to be used as an artifact and attach it in the release files.

Motivation

It could be helpful to centralize this operation with a required workflow like the one we setup for the JS/CSS linting step

Read more about those: https://github.com/pressbooks/reusable-workflows

This way we can apply regular updates in our PHP test matrix, Unit Tests and packaging meanwhile we pave the way for automated releases