Investigate Content-Encoding support

Bun has an option to upload pre-encoded data: https://bun.com/blog/bun-v1.3.7#s3-contentencoding-option

```js
const file = s3.file("my-bucket/data.json.gz");

await file.write(compressedData, { contentEncoding: "gzip" });

const bucket = s3.bucket("my-bucket");
await bucket.write("data.json.br", brotliData, { contentEncoding: "br" });
```

Maybe we could support that, too.