Add instructions option to speech request (#374)

* Add instructions field to speech request

* Update async-openai/src/types/audio.rs

* Update openapi.yaml

---------

Co-authored-by: Himanshu Neema <[email protected]>

Author: emchristiansen

async-openai/src/types/audio.rs

@@ -188,10 +188,16 @@ pub struct CreateSpeechRequest {
     /// One of the available [TTS models](https://platform.openai.com/docs/models/tts): `tts-1` or `tts-1-hd`
     pub model: SpeechModel,
 
-    /// The voice to use when generating the audio. Supported voices are `alloy`, `ash`, `coral`, `echo`, `fable`, `onyx`, `nova`, `sage` and `shimmer`.
+    /// The voice to use when generating the audio. Supported voices are `alloy`, `ash`, `coral`, `echo`, `fable`, `onyx`, `nova`, `sage`, `shimmer` and `verse`.
+
     /// Previews of the voices are available in the [Text to speech guide](https://platform.openai.com/docs/guides/text-to-speech#voice-options).
     pub voice: Voice,
 
+    /// Control the voice of your generated audio with additional instructions.
+    /// Does not work with `tts-1` or `tts-1-hd`.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub instructions: Option<String>,
+
     /// The format to audio in. Supported formats are `mp3`, `opus`, `aac`, `flac`, `wav`, and `pcm`.
     #[serde(skip_serializing_if = "Option::is_none")]
     pub response_format: Option<SpeechResponseFormat>,