fixing landing page layout on server render

Summary:
On the first render the landing page was missing a CSS class. This ls probably related to https://github.com/gatsbyjs/gatsby/issues/5136
It is fixed by wrapping the page in a <div>

Reviewed By: priteshrnandgaonkar

Differential Revision: D8660801

fbshipit-source-id: dd1ac4145831f2556e2c7ceeaddb2a423447f833

website/src/components/Playground/index.js

@@ -19,6 +19,7 @@ import PositionRecord from './PositionRecord';
 import LayoutRecord from './LayoutRecord';
 import Sidebar from './Sidebar';
 import {Row, Col, Button} from 'antd';
+import btoa from 'btoa';
 import type {LayoutRecordT} from './LayoutRecord';
 import type {Yoga$Direction} from 'yoga-layout';
 import './index.css';