Add hpainter.js demo for node

It shows how file can be opened and items are draw

Author: linev

demo/node/hpainter.js

@@ -0,0 +1,23 @@
+import { version, HierarchyPainter } from 'jsroot';
+
+
+console.log(`JSROOT version ${version}`);
+
+
+const hp = new HierarchyPainter('batch', null);
+
+hp.setDrawFunc((dom, obj, opt) => {
+   console.log(`trying to draw ${obj._typename}`);
+   return null;
+});
+
+await hp.openRootFile('https://root.cern/js/files/hsimple.root');
+
+// display of TH2 histogram
+await hp.display('hpxpy');
+
+await hp.expandItem('ntuple');
+
+// invoking TTree::Draw
+await hp.display('ntuple/pz');
+