Add Silero VAD (#313)

sherpa-onnx/python/sherpa_onnx/__init__.py

@@ -1,6 +1,16 @@
 from typing import Dict, List, Optional
 
-from _sherpa_onnx import Display, OfflineStream, OnlineStream
+from _sherpa_onnx import (
+    CircularBuffer,
+    Display,
+    OfflineStream,
+    OnlineStream,
+    SileroVadModelConfig,
+    SpeechSegment,
+    VadModel,
+    VadModelConfig,
+    VoiceActivityDetector,
+)
 
 from .offline_recognizer import OfflineRecognizer
 from .online_recognizer import OnlineRecognizer