Add guide for contributing to CI/CD configuration
What does this MR do and why?
It covers topics such as adding new keywords, inheritance patterns,
helper classes, the usage of the value
method,
feature flag implementation, and testing/validation practices.
https://main-ee-140459.docs.gitlab-review.app/ee/development/cicd/configuration.html
Ref #428920 (closed)
Edited by Furkan Ayhan