Add link to GitLab user profile on Contributors graph

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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
• Documentation
• Added to features.yml