Add all workflows

[sophiewigmore]

In #812 we added a few workflows to this repository.
We should look into adding the rest of the workflows from https://github.com/cloudfoundry/buildpacks-github-config/tree/main/buildpack to this buildpack.

Because the PHP buildpack has differences from the other CF buildpacks, some of the scripts and workflows may not work. We should investigate what will work, and pull in the appropriate files where we can.