Publish code coverage report with GitLab Pages

This post details how to configure SimpleCov for Ruby RSpec tests, generate HTML code coverage reports, and publish them using GitLab CI/CD and GitLab Pages. It outlines the `.gitlab-ci.yml` configuration for running tests, storing artifacts, and deploying the reports to GitLab Pages. It also covers how to handle parallel test execution by merging partial coverage reports and how to add a code coverage badge to the README.md file.