版本：2.1.0
- https://cdn.bootcdn.net/ajax/libs/loadCSS/2.1.0/cssrelpreload.js
- https://cdn.bootcdn.net/ajax/libs/loadCSS/2.1.0/cssrelpreload.min.js
- https://cdn.bootcdn.net/ajax/libs/loadCSS/2.1.0/loadCSS.js
- https://cdn.bootcdn.net/ajax/libs/loadCSS/2.1.0/loadCSS.min.js
- https://cdn.bootcdn.net/ajax/libs/loadCSS/2.1.0/onloadCSS.js
- https://cdn.bootcdn.net/ajax/libs/loadCSS/2.1.0/onloadCSS.min.js