Vite: Cannot use import statement outside a module

**Describe the bug**
I'm trying to use it in a SvelteKit project. But I'm getting "Cannot use import statement outside a module" on this line:
```javascript
import { toBlobURL, fetchFile } from "@ffmpeg/util"
```

**To Reproduce**
1. Install `@ffmpeg/ffmpeg` and `@ffmpeg/util` in a blank SvelteKit project.
2. In your `src/routes/+page.svelte` file, initialize ffmpeg.wasm:
```javascript
import { onMount } from "svelte";
import { FFmpeg } from "@ffmpeg/ffmpeg";
import { toBlobURL, fetchFile } from "@ffmpeg/util";
let loaded = false;

const ffmpeg = new FFmpeg();
ffmpeg.on("log", ({ message }) => {
console.log(message);
});

onMount(async () => {
const baseURL = "https://unpkg.com/@ffmpeg/core-mt@0.12.4/dist/esm";
await ffmpeg.load({
coreURL: await toBlobURL(`${baseURL}/ffmpeg-core.js`, "text/javascript"),
wasmURL: await toBlobURL(
`${baseURL}/ffmpeg-core.wasm`,
"application/wasm"
),
workerURL: await toBlobURL(
`${baseURL}/ffmpeg-core.worker.js`,
"text/javascript"
),
});
loaded = true;
});
```

**Error**
```
Cannot use import statement outside a module

...\node_modules\.pnpm\@ffmpeg+util@0.12.1\node_modules\@ffmpeg\util\dist\esm\index.js:1
import { ERROR_RESPONSE_BODY_READER, ERROR_INCOMPLETED_DOWNLOAD, } from "./errors.js";
^^^^^^
```

**Enviroment:**
- OS: Windows 11
- Browser: chrome
- Node Version: v18.17.1