Document the new GitLab CI pipeline that automatically applies Konflux Release CRs when release YAMLs are merged to main.

Should cover:
  - How the pipeline works (validate on MR, apply on merge)
  - Prerequisites (semi-linear merge strategy, KUBECONFIG_CONTENT CI variable)
  - How to add a new release (create YAML in <product>/<version>/releases/<release>/, open MR)
  - What to expect after merge (pipeline applies the CR, logs the PipelineRun link)

Acceptance Criteria:
  - README or dedicated doc in the repo explains the CI pipeline workflow
  - A contributor can understand how to use the pipeline without prior context