message: doc(styleguide): also updated Hello World example
diff: ```jsx static
  import React from 'react';
  import ReactDOM from 'react-dom';
  -import { AppRoot, View, Panel, PanelHeader, Header, Group, Cell } from '@vkontakte/vkui';
  +import { AppRoot, SplitLayout, SplitCol, View, Panel, PanelHeader, Header, Group, Cell } from '@vkontakte/vkui';
  import '@vkontakte/vkui/dist/vkui.css';
  function App() {
  return (
  <AppRoot>
  + <SplitLayout>
  + <SplitCol>
  <View activePanel="main">
  <Panel id="main">
  <PanelHeader>VKUI</PanelHeader>
  @@ -16,6 +18,8 @@ function App () {
  </Group>
  </Panel>
  </View>
  + </SplitCol>
  + </SplitLayout>
  </AppRoot>
  );
  }
  