inspired by jso0/html-webpack-cdn-plugin#1

Depends on #13

options.fallbackResolver

Type: string || function

Default: 'module-to-cdn' || 'module-to-jsdelivr'

Similar to resolver but the module will be loaded from this CDN only if the main CDN is experiencing issues

It will create a new file which will contains for each module:

window.React || document.write('<script src="https://unpkg.com/[email protected]/dist/react.js"><\/script>');

NOTE: resolver and fallback must both return a valid cdnConfig otherwise the module is ignored