Complete a CTRT revamp of the merge trains documentation
Problem to solve
The merge trains feature is pretty important for CI/CD, but documentation has not been fully brought up to our CTRT standards: https://docs.gitlab.com/ee/development/documentation/topic_types/
This is the last page in the merge request pipeline "series" that needs to be brought up to standards, and then we can close out the two related issues.
Edited by Marcel Amirault