added support for classnames on preview component
added support for classnames on preview component

storybooks/storybook,kadirahq/react-storybook,storybooks/storybook,storybooks/react-storybook,kadirahq/react-storybook,storybooks/react-storybook,storybooks/storybook,storybooks/storybook,storybooks/react-storybook,storybooks/storybook,storybooks/storybook,storybooks/react-storybook,storybooks/storybook