Add University link to home page

What does this MR do and why?

With the recent launch of GitLab University (https://university.gitlab.com/ - GitLab Team Members use incognito browser to see how the content on GitLab University appears to non-Team Members), this MR adds a new Get certified block, similar to the Get support block, to direct folks to the university site.

Screenshots, screen recordings, or links to review app

Before: https://docs.gitlab.com/	After: https://dianalogan-main-patch-e9da.docs.gitlab-review.app/index.html

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/doc/setup.md.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.