Promise not resolve on NativeAudio.preload

**Describe the bug**
Promise does not resolve on preloading Assets

**To Reproduce**
```ts
NativeAudio.preload({
assetId: 'sound.mp3',
assetPath: 'public/assets/sound.mp3',
audioChannelNum: 1,
isUrl: false,
})
.then(() => console.log('loaded'))
.catch(e => console.error(e))
```

**Expected behavior**
Promise should be resolve or fail

**Smartphone (please complete the following information):**
- iOS 15

**Additional context**
Add any other context about the problem here.

Start by reproducing the NativeAudio.preload example on iOS 15, then inspect the plugin entry point that handles preload requests. Trace both the success and failure paths; done means the returned Promise resolves when the asset loads or rejects when preloading fails.

Written by the indexing model from the issue text.