docs(s3): add Clever Cloud Cellar in supported services

Author: davlgd

docs/api/s3.md

@@ -327,6 +327,36 @@ const r2 = new S3Client({
 });
 ```
 
+### Using Bun's S3Client with Clever Cloud Cellar
+
+To use Bun's S3 client with [Clever Cloud Cellar]([https://developers.cloudflare.com/r2/](https://www.clever-cloud.com/developers/doc/addons/cellar/)), set `endpoint` to the Cellar endpoint in the `S3Client` constructor.
+
+```ts
+import { S3Client } from "bun";
+
+// Clever Cloud Cellar
+const r2 = new S3Client({
+  accessKeyId: "access-key",
+  secretAccessKey: "secret-key",
+  bucket: "my-bucket",
+  endpoint: "https://cellar-c2.services.clever-cloud.com",
+});
+```
+
+If you've linked a Cellar add-on to a Clever Cloud application, you can just use environment variables:
+
+```ts
+import { S3Client } from "bun";
+
+// Clever Cloud Cellar
+const r2 = new S3Client({
+  accessKeyId: process.env.CELLAR_ADDON_KEY_ID,
+  secretAccessKey: process.env.CELLAR_ADDON_KEY_SECRET,
+  bucket: "my-bucket",
+  endpoint: `https://${process.env.CELLAR_ADDON_HOST}`,
+});
+```
+
 ### Using Bun's S3Client with DigitalOcean Spaces
 
 To use Bun's S3 client with [DigitalOcean Spaces](https://www.digitalocean.com/products/spaces/), set `endpoint` to the DigitalOcean Spaces endpoint in the `S3Client` constructor.