paraBookmark(paras) {
    return {
      s: {
        path: lists.tail(dom.makeOffsetPath(lists.head(paras), this.sc)),
        offset: this.so,
      },
      e: {
        path: lists.tail(dom.makeOffsetPath(lists.last(paras), this.ec)),
        offset: this.eo,
      },
    };
  }
create offsetPath bookmark base on paragraph

@param {Node[]} paras