chore(examples): add old api examples

example/src_oldapi/Undirectional/CustomNode.tsx

@@ -0,0 +1,19 @@
+import React, { memo, FC, CSSProperties } from 'react';
+
+import { Handle, Position, NodeProps } from 'react-flow-renderer';
+
+const nodeStyles: CSSProperties = { padding: '10px 15px', border: '1px solid #ddd' };
+
+const CustomNode: FC<NodeProps> = ({ id }) => {
+  return (
+    <div style={nodeStyles}>
+      <div>node {id}</div>
+      <Handle type="source" id="left" position={Position.Left} />
+      <Handle type="source" id="right" position={Position.Right} />
+      <Handle type="source" id="top" position={Position.Top} />
+      <Handle type="source" id="bottom" position={Position.Bottom} />
+    </div>
+  );
+};
+
+export default memo(CustomNode);