Add link to GitLab user profile on Contributors graph
Please read this!
### Description
e.g. https://gitlab.com/gitlab-org/gitlab-ce/graphs/master shows all contributors. But when the contributor has a profile on GitLab, it's not linked.
### Proposal
Make the author names clickable if they have an account on GitLab.

### Feature checklist
Make sure these are completed before closing the issue,
with a link to the relevant commit.
- [ ] [Feature assurance](https://about.gitlab.com/handbook/product/#feature-assurance)
- [ ] Documentation
- [ ] Added to [features.yml](https://gitlab.com/gitlab-com/www-gitlab-com/blob/master/data/features.yml)