Modifier used to make sure the reference and its popper stay near each other\n   * without leaving any gap between the two. Especially useful when the arrow is\n   * enabled and you want to ensure that it points to its reference element.\n   * It cares only about the first axis. You can still have poppers with margin\n   * between the popper and its reference element.\n   * @memberof modifiers\n   * @inner\n   */\n  keepTogether: {\n    /** @prop {number} order=400 - Index used to define the order...