feat: add tts on account level (#366)

lib/tasks/lex.js

@@ -189,6 +189,7 @@ class Lex extends Task {
           this.logger.debug(`tts with ${this.vendor} ${this.voice}`);
           // eslint-disable-next-line no-unused-vars
           const {filePath, servedFromCache} = await synthAudio(stats, {
+            account_sid: cs.accountSid,
             text: msg,
             vendor: this.vendor,
             language: this.language,