feat(fonts): granular preload

src/content/docs/en/reference/experimental-flags/fonts.mdx

@@ -311,7 +311,7 @@ import { Font } from 'astro:assets';
 
 <p>
 
-**Type:** `boolean`<br />
+**Type:** `boolean | { weight?: string | number; style?: string; subset?: string }[]`<br />
 **Default:** `false`
 </p>
 
@@ -325,6 +325,36 @@ import { Font } from 'astro:assets';
 <Font cssVariable="--font-roboto" preload />
 ```
 
+With the `preload` directive, the browser will immediately begin downloading all possible font links during page load. 
+
+#### Granular preloads
+
+<p>
+<Since v="5.15.0" />
+</p>
+
+You may not always want to preload every font link, as this can block loading other important resources or may download fonts that are not needed for the current page. 
+
+To selectively control which font files are preloaded, you can provide an array of objects describing any combination of font `weight`, `style`, or `subset` to preload.
+
+The following example will only preload font files with a `400` weight or a `normal` style in the `latin` subset:
+
+```astro title="src/components/Head.astro" {7-10}
+---
+import { Font } from 'astro:assets';
+---
+
+<Font
+  cssVariable="--font-roboto"
+  preload={[
+    { subset: 'latin', style: 'normal' },
+    { weight: '400' },
+  ]}
+/>
+```
+
+Variable weight font files will be preloaded if any weight within its range is requested. For example, a font file for font weight `100 900` will be included when `400` is specified in a `preload` object.
+
 ## Accessing font data programmatically
 
 The `getFontData()` function is intended for retrieving lower-level font family data programmatically, for example, in an [API Route](/en/guides/endpoints/#server-endpoints-api-routes) or to generate your own meta tags.