Add a special GitLab markdown reference for milestones
It would be nice if it was possible to reference milestones by name through a special GitLab-flavored markdown reference.
For example:
- %8.6 would link to a milestone named "8.6" in the current project
- gitlab-org/gitlab-ce%8.6 would be a cross-project reference to a milestone named "8.6" in the "gitlab-ce" project in the "gitlab-org" namespace
- %*8.6 would link to the milestone named "8.6" in the current group
- gitlab-org%8.6 would be a cross-group reference to the milestone named "8.6" in the "gitlab-org" group
(This idea was also suggested on the deprecated feedback forum.)