fix: import the markdownRender style manually

Author: wewoor

stories/index.stories.tsx

@@ -1,6 +1,7 @@
 import * as React from 'react';
 import { storiesOf } from '@storybook/react';
 import { MarkdownRender } from 'dt-react-component';
+import 'dt-react-component/lib/markdownRender/style/style.css';
 
 import './style.scss';
 import { notShowProps } from './utils';