版本：
文件：
- https://cdn.bootcdn.net/ajax/libs/Buttons/2.0.0/css/buttons.css
- https://cdn.bootcdn.net/ajax/libs/Buttons/2.0.0/css/buttons.min.css
- https://cdn.bootcdn.net/ajax/libs/Buttons/2.0.0/js/buttons.js
- https://cdn.bootcdn.net/ajax/libs/Buttons/2.0.0/js/buttons.min.js