feat: add markdownlint.yaml configuration

mentioned in merge request gcp-cloud-run-app!155

mentioned in merge request gcp-secret-manager!65 (merged)

mentioned in merge request gcp-monitoring!30

mentioned in merge request ucam-gcp-secret!42 (merged)

mentioned in merge request gke-cluster!94

mentioned in merge request gcp-alert-snooze!73 (merged)

mentioned in merge request ucam-observe-remote-server!43

mentioned in merge request gcp-function!62 (merged)

mentioned in merge request gcp-cloud-run-function!62

mentioned in merge request gcp-alert-to-gitlab-issue!6

mentioned in merge request gcp-scheduled-script!76 (merged)

mentioned in merge request gcp-container-image-mirror!65 (merged)

mentioned in merge request ucam-faas-long!52 (merged)

mentioned in merge request gcp-site-monitoring!81 (merged)

mentioned in merge request gcp-notification-to-gitlab-issue!69 (merged)

mentioned in merge request ucam-faas!84 (merged)

mentioned in merge request gcp-pubsub-to-ms-teams!66 (merged)

mentioned in merge request ucam-minimal-gcp-monitoring!8