Add missing changelog item and add 8.6.1

[ci skip]

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
-v 8.6.0 (unreleased)
+v 8.6.1 (unreleased)
+
+
+v 8.6.0
   - Add ability to move issue to another project
   - Prevent tokens in the import URL to be showed by the UI
   - Fix bug where wrong commit ID was being used in a merge request diff to show old image (Stan Hu)
@@ -18,6 +21,7 @@ v 8.6.0 (unreleased)
     setup. A password can be provided during setup (see installation docs), or
     GitLab will ask the user to create a new one upon first visit.
   - Fix issue when pushing to projects ending in .wiki
+  - Properly display YAML front matter in Markdown
   - Add support for wiki with UTF-8 page names (Hiroyuki Sato)
   - Fix wiki search results point to raw source (Hiroyuki Sato)
   - Don't load all of GitLab in mail_room