types mismatch of `.process` in sync mode

jsdoc:
```js
   * @returns {Object<{html: String, tree: PostHTMLTree}>} - Sync Mode
   * @returns {Promise<{html: String, tree: PostHTMLTree}>} - Async Mode (default)
```


but `d.ts`:
```ts
process(html: string, options?: Options): Promise<Result<TMessage>>
```

Results in that even `sync` is set to `true`, the return type is still `Promise<Result<TMessage>>`.