Add hstack example

examples/node/hstack.js

@@ -0,0 +1,17 @@
+const fs = require('fs');
+const { createWorker } = require('../../src');
+
+const worker = createWorker({
+  logger: ({ message }) => console.log(message),
+});
+
+(async () => {
+  await worker.load();
+  console.log('Start hstack');
+  await worker.write('flame.avi', '../../tests/assets/flame.avi');
+  await worker.run('-i flame.avi -i flame.avi -filter_complex hstack flame.mp4');
+  const { data } = await worker.read('flame.mp4');
+  console.log('Complete hstack');
+  fs.writeFileSync('flame.mp4', Buffer.from(data));
+  await worker.terminate();
+})();