modal destroy (#2124)

* modal destroy

* document and typo

* remove blank line

components/modal/confirm.jsx

@@ -129,4 +129,8 @@ export default function confirm(config) {
   , div, function () {
     d = this;
   });
+
+  return {
+    destroy: close,
+  };
 }

components/modal/demo/manual.md

@@ -0,0 +1,23 @@
+---
+order: 7
+title: 手动移除
+---
+
+手动关闭modal。
+
+````jsx
+import { Modal, Button } from 'antd';
+
+function success() {
+  const modal = Modal.success({
+    title: '这是一条通知信息',
+    content: '一秒后自动移除',
+  });
+  setTimeout(() => modal.destroy(), 1000);
+}
+
+
+ReactDOM.render(<div>
+  <Button onClick={success}>成功提示</Button>
+</div>, mountNode);
+````