Add keyword spotting API for node-addon-api (#877)

scripts/node-addon-api/lib/keyword-spotter.js

@@ -0,0 +1,32 @@
+const addon = require('./addon.js');
+const streaming_asr = require('./streaming-asr.js');
+
+class KeywordSpotter {
+  constructor(config) {
+    this.handle = addon.createKeywordSpotter(config);
+    this.config = config
+  }
+
+  createStream() {
+    const handle = addon.createKeywordStream(this.handle);
+    return new streaming_asr.OnlineStream(handle);
+  }
+
+  isReady(stream) {
+    return addon.isKeywordStreamReady(this.handle, stream.handle);
+  }
+
+  decode(stream) {
+    addon.decodeKeywordStream(this.handle, stream.handle);
+  }
+
+  getResult(stream) {
+    const jsonStr = addon.getKeywordResultAsJson(this.handle, stream.handle);
+
+    return JSON.parse(jsonStr);
+  }
+}
+
+module.exports = {
+  KeywordSpotter,
+}