Adding StopSpeaking() to TextToSpeechManager

Author: keveleigh

Assets/HoloToolkit/Utilities/Scripts/TextToSpeechManager.cs

@@ -382,6 +382,17 @@ public void SpeakText(string text)
             #endif
         }
 
+        /// <summary>
+        /// Stops text-to-speech playback.
+        /// </summary>
+        public void StopSpeaking()
+        {
+            if (audioSource.isPlaying)
+            {
+                audioSource.Stop();
+            }
+        }
+
         /// <summary>
         /// Gets or sets the audio source where speech will be played.
         /// </summary>