Add an overview of pre and release environments
What does this MR do?
Adds a generic overview of pre and release environments
The 17.0 major release is coming on May 16, 2024! This version brings many exciting improvements to GitLab, but also removes some deprecated features. We are introducing three breaking change windows during which we expect breaking changes to be deployed to GitLab.com. You can read more about it on our blogpost. The third breaking change window begins 2024-05-06 09:00 UTC and ends 2024-05-08 22:00 UTC.