ci(danger): setup reviewers roulette
This MR adds a reviewers roulette to GitLab UI's Danger rules. Most of the code here has been copied from GitLab's roulette, with a few adjustments to better fit GitLab UI's requirements.
For each detected change categories we pick a reviewer and a maintainer from the GitLab project. Whatever the kind of change, we pick a frontend reviewer from the GitLab UI project as the GitLab UI WG approver.
Edited by Paul Gascou-Vaillancourt