Add guidelines for introducing a change in production

Extracted from the old change checklist.

After https://gitlab.com/gitlab-com/infrastructure/merge_requests/17 got merged, we need to gather all the guidelines that were in the old checklist into a single place. Why not the handbook?

Thanks @pcarranza

Not sure why we didn't merge this, but now it is outdated with the issue checklist instead, right @pcarranza ?

@ernstvn as long as we have something in the handbook pointing at the issue template, yes.

OK, closing in favor of https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/7589

closed

mentioned in merge request !7589 (merged)