support whisper instructions (#1198)

* support whisper instructions

* wip

* update speech utils and verb specification

lib/tasks/tts-task.js

@@ -21,6 +21,7 @@ class TtsTask extends Task {
     this.synthesizer = this.data.synthesizer || {};
     this.disableTtsCache = this.data.disableTtsCache;
     this.options = this.synthesizer.options || {};
+    this.instructions = this.data.instructions;
   }
 
   async exec(cs) {
@@ -262,6 +263,7 @@ class TtsTask extends Task {
           const {filePath, servedFromCache, rtt} = await synthAudio(stats, {
             account_sid,
             text,
+            instructions: this.instructions,
             vendor,
             language,
             voice,