Gitter room on issue
After it is possible to create gitter room for a project (gitlab-ce#29755), then it would be also beneficial to create gitter room for a project issue. For example in the Drupal community many developers are collaborating on the same issue. Dedicated chat can speed up the resolution of the issue. The chat should be created as a "sub chat room" of the project chat room. The UI should be similar and as easy to use as the project room functionality.