Enable SLO-as-Code with Nobl9 and GitLab

What this post added

This post introduces an integration between GitLab CI and Nobl9 to enable SLO-as-Code. It details the steps to configure CI/CD variables (CLIENT_ID, CLIENT_SECRET, ACCESS_TOKEN, PROJECT, SLOCTL_YML) and provides a `.gitlab-ci.yml` configuration that uses the `nobl9/nobl9-ci-template` project to push SLO definitions to Nobl9 via the `sloctl` command-line tool. This automates the process of keeping SLO definitions synchronized between the code repository and Nobl9.