[New Feature] Load config from file `svelte-sitemap.cjs`

## Feature idea
I want to try the possibility of loading the config from a file

- This should become the main and recommended method
- The CLI version should remain untouched

## Proposal

`./svelte-sitemap.cjs`
```javascript
module.exports = {
  domain: 'https://www.example.com',
  resetTime: false,
  debug: true
};

```

Let's discuss here ;)