message: update UnderlineNav docs
diff: @@ -35,8 +35,10 @@ export default {
  Using <Text mono>{'<NavLink>'}</Text> from react-router
  </ExampleHeading>
  <p>
  - To use UnderlineNav with <Link href="https://github.com/ReactTraining/react-router">react-router</Link> or <Link href="https://www.npmjs.com/package/react-router-dom">react-router-dom</Link>, pass <Text mono>{'tag={NavLink}'}</Text> and omit the <Text mono>selected</Text> prop.
  - This ensures that the NavLink gets <Text mono>activeClassName='selected'</Text>.
  + To use UnderlineNav with <Link href="https://github.com/ReactTraining/react-router">react-router</Link> or{' '}
  + <Link href="https://www.npmjs.com/package/react-router-dom">react-router-dom</Link>, pass{' '}
  + <Text mono>{'tag={NavLink}'}</Text> and omit the <Text mono>selected</Text> prop. This ensures that the
  + NavLink gets <Text mono>activeClassName='selected'</Text>.
  </p>
  <LiveEditor code={navLinkExample} scope={{UnderlineNav, UnderlineNavLink, NavLink}} />
  </Block>
  