版本：
文件：
- https://cdn.bootcdn.net/ajax/libs/progressively/1.2.5/progressively.css
- https://cdn.bootcdn.net/ajax/libs/progressively/1.2.5/progressively.js
- https://cdn.bootcdn.net/ajax/libs/progressively/1.2.5/progressively.min.css
- https://cdn.bootcdn.net/ajax/libs/progressively/1.2.5/progressively.min.js