Add http link to changelog to help page

Description

On the Help page you are notified of a new Gitlab version, and that the current used one is outdated. It would be helpful to get to the changelog via hyperlink, so the admin can check whats been implemented or fixed since his/her currently running version.

Proposal

Add hyperlink to public changelog to help page of gitlab.

Links / references

CE changelog https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md