fonts: clarify adobe id loading (#12730)

Co-authored-by: Sarah Rainsberger <[email protected]>

Author: florian-lefebvre

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

@@ -152,7 +152,9 @@ body {
 
 ## Available remote font providers
 
-Astro re-exports most [unifont](https://github.com/unjs/unifont/) providers. The following have built-in support:
+Astro re-exports most [unifont](https://github.com/unjs/unifont/) providers. You can also [make a custom Astro font provider](#build-your-own-font-provider) for any unifont provider.
+
+The following providers have built-in support:
 
 - [Adobe](https://fonts.adobe.com/)
 - [Bunny](https://fonts.bunny.net/)
@@ -167,9 +169,11 @@ To use a built-in remote provider, configure `provider` with the appropriate val
 <TabItem label="Adobe">
 
 ```js
-provider: fontProviders.adobe({ id: process.env.ADOBE_ID })
+provider: fontProviders.adobe({ id: 'your-id' })
 ```
 
+Pass the Adobe font provider an ID loaded as an [environment variable in your Astro config file](/en/guides/environment-variables/#in-the-astro-config-file).
+
 </TabItem>
 
 <TabItem label="Bunny">
@@ -216,8 +220,6 @@ provider: fontProviders.google({
 
 </Tabs>
 
-You can also [make a custom Astro font provider](#build-your-own-font-provider) for any unifont provider.
-
 ## Usage examples
 
 ```js title="astro.config.mjs"