fetch() does not work with dot files

### Problem description
Dot files are not found when attempting to `fetch()` them.

### Expected behavior
Dot files should be `fetch()`-able. A particular use case is reading a `.env` file in the root of the project (as https://www.npmjs.com/package/dotenv does it).

### Environment

- Tabris.js version: 3.7.1
- OS: can be reproduced on both Android and iOS

### Code snippet

```js
(async () => {
console.log(await (await fetch('./.env')).text()); // doesn't work
console.log(await (await fetch('./env')).text()); // works
})().catch(console.error);
```