getRect(element) {
    element = element || (is.element(this.target) ? this.target : null);

    if (is.string(this.target)) {
      element = element || this._context.querySelector(this.target);
    }

    return getElementRect(element);
  }
The default function to get an Interactables bounding rect. Can be
overridden using {@link Interactable.rectChecker}.

@param {Element} [element] The element to measure.
@return {Interact.Rect} The object's bounding rectangle.