chore(examples): add old api examples

example/src_oldapi/DragNDrop/Sidebar.tsx

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+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;

example/src_oldapi/DragNDrop/dnd.css

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+.dndflow {
+  flex-direction: column;
+  display: flex;
+  height: 100%;
+}
+
+.dndflow aside {
+  border-right: 1px solid #eee;
+  padding: 15px 10px;
+  font-size: 12px;
+  background: #fcfcfc;
+}
+
+.dndflow aside > * {
+  margin-bottom: 10px;
+  cursor: grab;
+}
+
+.dndflow aside .description {
+  margin-bottom: 10px;
+}
+
+.dndflow .reactflow-wrapper {
+  flex-grow: 1;
+  height: 100%;
+}
+
+@media screen and (min-width: 768px) {
+  .dndflow {
+    flex-direction: row;
+  }
+
+  .dndflow aside {
+    width: 20%;
+    max-width: 180px;
+  }
+}

example/src_oldapi/DragNDrop/index.tsx

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+import React, { useState, DragEvent } from 'react';
+import ReactFlow, {
+  ReactFlowProvider,
+  addEdge,
+  removeElements,
+  Controls,
+  OnLoadParams,
+  Elements,
+  Connection,
+  Edge,
+  ElementId,
+  Node,
+} from 'react-flow-renderer';
+
+import Sidebar from './Sidebar';
+
+import './dnd.css';
+
+const initialElements = [{ id: '1', type: 'input', data: { label: 'input node' }, position: { x: 250, y: 5 } }];
+
+const onDragOver = (event: DragEvent) => {
+  event.preventDefault();
+  event.dataTransfer.dropEffect = 'move';
+};
+
+let id = 0;
+const getId = (): ElementId => `dndnode_${id++}`;
+
+const DnDFlow = () => {
+  const [reactFlowInstance, setReactFlowInstance] = useState<OnLoadParams>();
+  const [elements, setElements] = useState<Elements>(initialElements);
+
+  const onConnect = (params: Connection | Edge) => setElements((els) => addEdge(params, els));
+  const onElementsRemove = (elementsToRemove: Elements) => setElements((els) => removeElements(elementsToRemove, els));
+  const onLoad = (_reactFlowInstance: OnLoadParams) => setReactFlowInstance(_reactFlowInstance);
+
+  const onDrop = (event: DragEvent) => {
+    event.preventDefault();
+
+    if (reactFlowInstance) {
+      const type = event.dataTransfer.getData('application/reactflow');
+      const position = reactFlowInstance.project({ x: event.clientX, y: event.clientY - 40 });
+      const newNode: Node = {
+        id: getId(),
+        type,
+        position,
+        data: { label: `${type} node` },
+      };
+
+      setElements((es) => es.concat(newNode));
+    }
+  };
+
+  return (
+    <div className="dndflow">
+      <ReactFlowProvider>
+        <div className="reactflow-wrapper">
+          <ReactFlow
+            elements={elements}
+            onConnect={onConnect}
+            onElementsRemove={onElementsRemove}
+            onLoad={onLoad}
+            onDrop={onDrop}
+            onDragOver={onDragOver}
+          >
+            <Controls />
+          </ReactFlow>
+        </div>
+        <Sidebar />
+      </ReactFlowProvider>
+    </div>
+  );
+};
+
+export default DnDFlow;