Add regular expression attribute to project hook API

According to https://docs.gitlab.com/ee/api/projects.html#add-project-hook documentation, we can add Push events -> Wildcard Pattern trigger for project webhook via API using the push_events_branch_filter string attribute. Can you please add an attribute for Regular expression too?

For some reason "Regular expression" is not reflected in API