add VAD disclaimer

requirements.txt

@@ -10,6 +10,7 @@ nlpaug
 pyyaml
 kapre
 
+# Silero VAD requirements
 torch
 torchaudio
 soundfile

src/audio/silero_vad/README.md

+This subfolder contains code and a pytorch model drawn from the [Silero VAD repository](https://github.com/snakers4/silero-vad).
+We slightly modified the code in order to feed the output of the pytorch model into Auditok's tokenization method.
\ No newline at end of file