Repair a security pipeline for GitHub Actions and GitLab CI: reference solution

Open this only after you have attempted the repair in the exercise download.

1. Extract this archive into the folder where you extracted security-pipeline.zip.
   It adds this file, reference.github.yml and reference.gitlab-ci.yml, and changes none of your files.
2. Follow the reference commands in that folder's README.txt; they select the
   reference with EXERCISE_MODULE=reference or a --reference option.
3. Compare reference.github.yml and reference.gitlab-ci.yml with your exercise files. A different repair can still be
   correct: the tests, not the reference text, define the required behavior.
