message: position Header
diff: import React from 'react'
  import Octicon, {MarkGithub} from '@githubprimer/octicons-react'
  import NextLink from 'next/link'
  -import {Text, FlexContainer, Button} from '../../src'
  +import {Text, FlexContainer, Button, Sticky} from '../../src'
  /*
  import {name, repository, version} from '../../package.json'
  @@ -11,6 +11,7 @@ const releaseURL = `https://github.com/${repository}/releases/v${version}`
  */
  const Header = () => (
  + <Sticky zIndex={100}>
  <FlexContainer mr={1} p={1} alignItems="center" justifyContent="space-between" bg="black" color="white">
  <FlexContainer ml={4} alignItems="center">
  <Octicon size="medium" icon={MarkGithub} className="mr-3" />
  @@ -39,6 +40,7 @@ const Header = () => (
  </NextLink>
  </div>
  </FlexContainer>
  + </Sticky>
  )
  export default Header
  