How to access Neural voices?

Hi there,

First, let me say this is an awesome package, thank you.

I just installed the package and I'm testing it out but I can only generate Standard voices. Is it possible to have access to Neural voices instead?

Also, how can I get the path to the output.mp3 file? I need the path to save it into the database.

$path = TextToSpeech::saveTo('output.mp3') ->convert('hello world', ['engine' => 'neural']);

AWS_VOICE_ID=Daniel