Push event for PullRequestTimeline


Currently, there are Commit objects on timelines, but it is missing information for when a push happened. This includes extra information such as when the push happened, who pushed it, etc. In addition, a branch may have been rewound to take commits off of it. In this case there are no new commits to show, but there is a push. It would be nice if the new Push type for the Checks preview could be added to the timeline.