message: add home page link, dry up top nav
diff: import React from 'react'
  import PropTypes from 'prop-types'
  -import Octicon, {Package} from '@githubprimer/octicons-react'
  +import Octicon, {Package, Paintcan} from '@githubprimer/octicons-react'
  import {NavLink} from 'react-router-dom'
  import {Styles} from './doc-components'
  import {Box, Link, Sticky, Text, UnderlineNav, UnderlineNavLink} from '../src'
  @@ -9,12 +9,17 @@ import {name, repository, version} from '../package.json'
  const pkg = `${name}@${version}`
  const releaseURL = `https://github.com/${repository}/releases/v${version}`
  +function TopNavLink(props) {
  + return <UnderlineNavLink is={NavLink} px={3} {...props} />
  +}
  +
  export default function Page({render}) {
  return (
  <React.Fragment>
  <Sticky bg="white" zIndex={100}>
  <UnderlineNav
  pl={3}
  + mb={3}
  actions={
  <Text color="gray.5" fontFamily="mono" px={4}>
  <Octicon icon={Package} className="mr-2" />
  @@ -22,15 +27,19 @@ export default function Page({render}) {
  </Text>
  }
  >
  - <UnderlineNavLink is={NavLink} to="/components" px={3}>
  + <TopNavLink to="/" exact>
  + <Octicon icon={Paintcan} size={20} />
  + <Text ml={2}>Primer</Text>
  + </TopNavLink>
  + <TopNavLink to="/components">
  Components
  - </UnderlineNavLink>
  - <UnderlineNavLink is={NavLink} to="/demos" px={3}>
  + </TopNavLink>
  + <TopNavLink to="/demos">
  Demos
  - </UnderlineNavLink>
  - <UnderlineNavLink is={NavLink} to="/sandbox" px={3}>
  + </TopNavLink>
  + <TopNavLink to="/sandbox">
  Sandbox
  - </UnderlineNavLink>
  + </TopNavLink>
  </UnderlineNav>
  </Sticky>
  <Box p={3}>{render()}</Box>
  