Blog post: Merge request reviewers blog post 2020-10-12

Closes #9238 (closed)

Review app: https://dgruesso-reviewers-blog-post.about.gitlab-review.app/blog/2020/10/12/merge-request-reviewers/index.html

Checklist for writer

• Link to issue added, and set to close when this MR is merged
• Add disclaimer copy to the top of your blog post file: https://about.gitlab.com/handbook/marketing/blog/unfiltered/#link-to-disclaimer
• Blog post file formatted correctly, including any accompanying images
• unfiltered category entered in frontmatter
• Review app checked for any formatting issues
• Reviewed by fellow team member
• Assign to someone on your team with maintainer access to merge (no need to assign to an Editorial team member)