Add VAD example for Dart API (#996)

dart-api-examples/vad/run.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+set -ex
+
+dart pub get
+
+
+if [[ ! -f ./silero_vad.onnx ]]; then
+  curl -SL -O https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/silero_vad.onnx
+fi
+
+if [[ ! -f ./lei-jun-test.wav ]]; then
+  curl -SL -O https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/lei-jun-test.wav
+fi
+
+dart run \
+  ./bin/vad.dart \
+  --silero-vad ./silero_vad.onnx \
+  --input-wav ./lei-jun-test.wav \
+  --output-wav ./lei-jun-test-no-silence.wav
+
+ls -lh *.wav