How can I upvote a feature idea for GitLab to offer a hostest Mattermost service for GitLab users?

Will it be available to gitlab.org projects ?

Hi @jigarshah, while the Mattermost team would love to see a hosted Mattermost version for GitLab.com users, it’s the decision of the GitLab team how and when to offer one.

Feature ideas for GitLab can be shared at http://feedback.gitlab.com/forums/176466-general