chore(examples): add old api examples

example/src_oldapi/DragNDrop/Sidebar.tsx

@@ -0,0 +1,25 @@
+import React, { DragEvent } from 'react';
+
+const onDragStart = (event: DragEvent, nodeType: string) => {
+  event.dataTransfer.setData('application/reactflow', nodeType);
+  event.dataTransfer.effectAllowed = 'move';
+};
+
+const Sidebar = () => {
+  return (
+    <aside>
+      <div className="description">You can drag these nodes to the pane on the left.</div>
+      <div className="react-flow__node-input" onDragStart={(event: DragEvent) => onDragStart(event, 'input')} draggable>
+        Input Node
+      </div>
+      <div className="react-flow__node-default" onDragStart={(event: DragEvent) => onDragStart(event, 'default')} draggable>
+        Default Node
+      </div>
+      <div className="react-flow__node-output" onDragStart={(event: DragEvent) => onDragStart(event, 'output')} draggable>
+        Output Node
+      </div>
+    </aside>
+  );
+};
+
+export default Sidebar;