message: fix: ignore document for firefox
diff: @@ -219,7 +219,7 @@ export default class MoveableManager<T = {}>
  * });
  */
  public isMoveableElement(target: Element) {
  - return target && (target.getAttribute("class") || "").indexOf(PREFIX) > -1;
  + return target && (target.getAttribute?.("class") || "").indexOf(PREFIX) > -1;
  }
  /**
  * You can drag start the Moveable through the external `MouseEvent`or `TouchEvent`. (Angular: ngDragStart)
  