This commit adds a new `MarkAsReadAlertControllerSourceType` protocol to which `CGRect`, `UIView`, and `UIBarButtonItem` conform to. The `MarkAsReadAlertController` now presents an action sheet for mark as read, mark above as read, and mark below as read. The above is used for the `popoverPresentationController`’s `barButtonItem`, `sourceRect`, or `sourceView` as needed.