Add UX reviewer/maintainer to Danger bot

What does this MR do and why?

Adds product design team members to the danger-review as a roulette. If a merge request has both a UX Community contribution label applied to it, then Danger bot will suggest a designer at random to review the change.

Note: Each designer must have the specialty added to their yml gitlab-com/www-gitlab-com!79769 (merged)

projects:
  gitlab: reviewer UX

Screenshots

How to set up and validate locally

Rerun the danger-review job with different labels applied or removed

MR 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 MR.

Related #322911, gitlab-design#1557 (closed)