Allow to override flatpak bundle name

### Pre-flight checklist

- [x] I have read the [contribution documentation](https://github.com/electron/forge/blob/main/CONTRIBUTING.md) for this project.
- [x] I agree to follow the [code of conduct](https://github.com/electron/electron/blob/main/CODE_OF_CONDUCT.md) that this project uses.
- [x] I have searched the issue tracker for a feature request that matches the one I want to file, without success.

### Problem description

It would be helpful to be able to override `flatpak` bundle name.

Currently name is hardcoded: https://github.com/malept/electron-installer-flatpak/blob/d066e8b2960b167e835316c72f642e972e097756/src/installer.js#L143-L145

```js
const name = `${this.appIdentifier}_${this.options.branch}_${this.options.arch}.flatpak`
const dest = this.options.rename(this.options.dest, name)
```

### Proposed solution

Allow to specify `artifactName`

### Alternatives considered

I don't know

### Additional information

_No response_