styleguide.torproject.org: migrate from Jenkins to GitLab CI

• include ci-templates lektor.yml job
• site builds and works in gitlab pages
• add the deploy-static job and SSH key to GitLab CI
• deploy the SSH key and static site in Puppet
• run the deploy-static job, make sure the site still works and was deployed properly (curl -sI https://example.torproject.org/ | grep -i Last-Modified)
• archive the repo on gitolite
• remove the old site on staticiforme
• fully retire the Jenkins jobs