add a comment about how to download silero_vad.onnx (#346)

@@ -11,6 +11,14 @@ Supported file formats are those supported by ffmpeg; for instance,
 
 Note that you need a non-streaming model for this script.
 
+Please visit
+https://github.com/snakers4/silero-vad/blob/master/files/silero_vad.onnx
+to download silero_vad.onnx
+
+For instance,
+
+wget https://github.com/snakers4/silero-vad/raw/master/files/silero_vad.onnx
+
 (1) For paraformer
 
     ./python-api-examples/generate-subtitles.py  \