docs: fix polyfill mdx

docs/docs/tutorials/installation.mdx

@@ -142,6 +142,8 @@ yarn add @egjs/svelte-flicking
 </Tabs>
 
 ## CDN Links
+Unlike individual or internal cases, CDN has unpredictable problems with services, so it is better to use your own files.
+
 ### packaged(with dependencies)
 ```html
 <!-- unpkg -->

docs/docs/tutorials/polyfills.mdx

@@ -6,6 +6,7 @@ custom_edit_url: null
 sidebar_position: 6
 ---
 
+### Before
 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.
@@ -14,4 +15,28 @@ So, only es6 Promise is needed to run Flicking on the older browsers.
 <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/es6-promise/dist/es6-promise.auto.js"></script>
 ```
 
+Adding the above script will make Flicking run on the older browsers.
+
+### After
+
+
+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 (For personal or internal use)
+```html
+<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/es6-promise/dist/es6-promise.auto.js"></script>
+```
+* How to use it yourself (Unlike individual or internal cases, CDN has unpredictable problems with services, so it is better to use your own files.)
+```
+# Download
+https://cdn.jsdelivr.net/npm/es6-promise/dist/es6-promise.auto.js
+```
+* How to use it via module (The pollution of the global scope)
+```js
+require('es6-promise').polyfill();
+```
+
+
 Adding the above script will make Flicking run on the older browsers.

docs/docs/tutorials/quick-start.mdx

@@ -23,7 +23,7 @@ import TabItem from '@theme/TabItem';
   ]}>
   <TabItem value="js">
 
-Add the script/CSS to the page.
+Add the script/CSS to the page. (Unlike individual or internal cases, CDN has unpredictable problems with services, so it is better to use your own files.)
 ```html
 <script src="https://unpkg.com/@egjs/flicking/dist/flicking.pkgd.min.js" crossorigin="anonymous"></script>
 <link rel="stylesheet" href="https://unpkg.com/@egjs/flicking/dist/flicking.css" crossorigin="anonymous" />