fix: fix polyfill mdx

docs/docs/tutorials/polyfills.mdx

@@ -24,7 +24,7 @@ Flicking is based on es5 and additionally needs es6 Promise to work properly.
 es5 is basically supported on IE9+ ([Source](http://kangax.github.io/compat-table/es5/))
 So, only es6 Promise is needed to run Flicking on the older browsers.
 
-* How to use it via CDN
+* How to use it via CDN (For personal or internal use)
 ```html
 <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/es6-promise/dist/es6-promise.auto.js"></script>
 ```