Note when vuln reference was added

doc/user/markdown.md

@@ -431,7 +431,7 @@ GFM recognizes the following:
 | merge request                   | `!123`                     | `namespace/project!123`                 | `project!123`                  |
 | snippet                         | `$123`                     | `namespace/project$123`                 | `project$123`                  |
 | epic **(ULTIMATE)**             | `&123`                     | `group1/subgroup&123`                   |                                |
-| vulnerability **(ULTIMATE)**    | `[vulnerability:123]`      | `[vulnerability:namespace/project/123]` | `[vulnerability:project/123]`  |
+| vulnerability **(ULTIMATE)** (1)| `[vulnerability:123]`      | `[vulnerability:namespace/project/123]` | `[vulnerability:project/123]`  |
 | label by ID                     | `~123`                     | `namespace/project~123`                 | `project~123`                  |
 | one-word label by name          | `~bug`                     | `namespace/project~bug`                 | `project~bug`                  |
 | multi-word label by name        | `~"feature request"`       | `namespace/project~"feature request"`   | `project~"feature request"`    |
@@ -445,6 +445,8 @@ GFM recognizes the following:
 | repository file line references | `[README](doc/README#L13)` |                                         |                                |
 | [alert](../operations/incident_management/alerts.md) | `^alert#123` | `namespace/project^alert#123`    | `project^alert#123`            |
 
+1. [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/222483) in GitLab 13.7.
+
 For example, referencing an issue by using `#123` will format the output as a link
 to issue number 123 with text `#123`. Likewise, a link to issue number 123 will be
 recognized and formatted with text `#123`.