Add CI/CD pipeline to deploy playbook

See

• https://stackoverflow.com/questions/63266075/how-to-run-ansible-playbook-from-gitlab-ci
• https://framagit.org/ploc/home-hosting-ansible
• https://about.gitlab.com/blog/2020/12/10/basics-of-gitlab-ci-updated/
• https://docs.gitlab.com/ee/ci/variables/predefined_variables.html
• https://blog.callr.tech/gitlab-ansible-docker-ci-cd/
• https://www.bevuta.com/en/blog/continuous-delivery-with-gitlab-ci-and-ansible-part-1/
• https://medium.com/@keirwhitlock/use-molecule-gitlab-ci-to-automate-testing-of-ansible-roles-9d745cd89db1