Link GitLab Review Workload Dashboard in Danger Reviewer Roulette

Just in case folks want more options.

danger/roulette/Dangerfile

@@ -15,7 +15,8 @@ CATEGORY_TABLE_HEADER = <<MARKDOWN
 To spread load more evenly across eligible reviewers, Danger has picked a candidate for each
 review slot, based on their timezone. Feel free to
 [override these selections](https://about.gitlab.com/handbook/engineering/projects/#gitlab)
-if you think someone else would be better-suited, or the chosen person is unavailable.
+if you think someone else would be better-suited
+or use the [GitLab Review Workload Dashboard](https://gitlab-org.gitlab.io/gitlab-roulette/) to find other available reviewers.
 
 To read more on how to use the reviewer roulette, please take a look at the
 [Engineering workflow](https://about.gitlab.com/handbook/engineering/workflow/#basics)