修复 connectForm 高阶组件 ref 透传 (#450)

* feat: 添加卡片类型的 theme

* feat: 调整圆角

* feat: 移除示例中的 theme

* fix: forward ref 透传 ref
Co-authored-by: N柏丘 <zhaolin.zhaolin@alibaba-inc.com>

packages/form-render/src/connectForm.js

-import React from 'react';
+import React, { forwardRef } from 'react';
 import useForm from './useForm';
 
 const connectForm = Component => {
-  return props => {
+  return forwardRef((props, ref) => {
     const form = useForm();
-    return <Component {...props} form={form} />;
-  };
+    return <Component ref={ref} {...props} form={form} />;
+  });
 };
 
 export default connectForm;