Add multiple cdn

src/content/docs/en/reference/configuration-reference.mdx

@@ -492,7 +492,7 @@ Specifies the directory in the build output where Astro-generated assets (bundle
 
 <p>
 
-**Type:** `string`<br />
+**Type:** `string | Record.<string, string>`<br />
 **Default:** `undefined`<br />
 <Since v="2.2.0" />
 </p>
@@ -512,6 +512,31 @@ To rename the `_astro` path, specify a new directory in `build.assets`.
 }
 ```
 
+#### defaultAssetsPrefix
+
+<p>
+
+**Type:** `string`<br />
+**Default:** `''`<br />
+<Since v="4.5.0" />
+</p>
+
+If your static files are served from different CDNs, you can configure `build.assetsPrefix` to use unique prefix paths for each CDN based on the file extension requested. `defaultAssetsPrefix` is used to fetch all other file extensions not defined.
+
+The following example shows `.js` files served from `https://js.cdn.example.com` and `.css` files served from `https://css.cdn.example.com`. All other assets will be served from `https://cdn.example.com`.
+
+```js
+{
+  build: {
+    assetsPrefix: {
+      'js': 'https://js.cdn.example.com',
+      'css': 'https://css.cdn.example.com',
+      'defaultAssetsPrefix': 'https://cdn.example.com'
+    }
+  }
+}
+```
+
 ### build.serverEntry
 
 <p>