Add toAudio macro to Stringable

[nhedger]

Note

AI assistance was used for this PR

Warning

Depends on #263 being merged because timeout support is baked in.

Description

This PR adds a toAudio macro to Stringable.

Examples

Str::of

# Short
$response = Str::of('Hello world')->toAudio(timeout: 45);

# Long
$response = Str::of('Hello world')->toAudio(
  provider: Lab::ElevenLabs,
  voice: 'alloy',
  instructions: 'Speak slowly',
  model: 'custom-model',
  timeout: 45,
);

[taylorotwell]

It looks like this includes the changes from the other PR.

[nhedger]

Should be all good now @taylorotwell