It would be useful to be able to trigger a build if the PR reviewer list is changed after the PR is first opened. This happens pretty commonly, so for users who have a build workflow that is partly organized around reviewers, support for this hook event would be useful. Relevant code is here: https://github.com/jenkinsci/bitbucket-branch-source-plugin/blob/cloudbees-bitbucket-branch-source-2.4.4/src/main/java/com/cloudbees/jenkins/plugins/bitbucket/hooks/HookEventType.java