Merge branch 'jt/port-ci-whitespace-check-to-gitlab'

The "whitespace check" task that was enabled for GitHub Actions CI has been ported to GitLab CI. * jt/port-ci-whitespace-check-to-gitlab: gitlab-ci: add whitespace error check ci: make the whitespace report optional ci: separate whitespace check script github-ci: fix link to whitespace error ci: pre-collapse GitLab CI sections