message: fix sidenav component
diff: import React from 'react'
  -import {NavLink} from 'mdx-docs'
  -import {Text, Link, Box} from '../../src'
  +import Link from 'next/link'
  +import {Text, Box} from '../../src'
  const SideNav = () =>
  <Box mt={4} ml={4}>
  - <NavLink href="/getting-started">Getting Started</NavLink>
  - <NavLink href="/system-props">System Props</NavLink>
  - <NavLink href="/primer-theme">Primer Theme</NavLink>
  - <Box mt={2} mb={3}><Text fontWeight='bold'>Components</Text></Box>
  - <Box mb={1}><Link nounderline scheme="gray-dark" pl={4} href="/components/avatar">Avatar</Link></Box>
  + <Link href="/getting-started">
  + <Text is="p" fontWeight='bold'>Getting Started</Text>
  + </Link>
  + <Link href="/system-props">
  + <Text is="p" fontWeight='bold'>System Props</Text>
  + </Link>
  + <Link href="/primer-theme">
  + <Text is="p" fontWeight='bold'>Primer Theme</Text>
  + </Link>
  + <Box mt={2} mb={3}>
  + <Text is="p" fontWeight='bold'>Components</Text>
  + </Box>
  + <Box mb={1}>
  + <Link href="/components/avatar">
  + <Text color="black" pl={4}>Avatar</Text>
  + </Link>
  + </Box>
  </Box>
  export default SideNav
  