feat(Android): Expose error code (#302)

Author: Arjanvanmaren

android/src/main/java/com/wenkesj/voice/VoiceModule.java

@@ -307,6 +307,7 @@ public void onError(int errorCode) {
     String errorMessage = String.format("%d/%s", errorCode, getErrorText(errorCode));
     WritableMap error = Arguments.createMap();
     error.putString("message", errorMessage);
+    error.putString("code", String.valueOf(errorCode));
     WritableMap event = Arguments.createMap();
     event.putMap("error", error);
     sendEvent("onSpeechError", event);