message: update _app js
diff: @@ -4,7 +4,7 @@ import PropTypes from 'prop-types'
  import {NavLink} from 'react-router-dom'
  import Styles from './doc-components/Styles'
  import Octicon, {Package} from '@githubprimer/octicons-react'
  -import {Block, Link, Text, UnderlineNav, UnderlineNavLink, theme} from '../src'
  +import {Box, Link, Text, UnderlineNav, UnderlineNavLink, theme} from '../src'
  import {name, repository, version} from '../package.json'
  const pkg = `${name}@${version}`
  @@ -15,7 +15,7 @@ export default function Page({render}) {
  <React.Fragment>
  <Styles />
  <ThemeProvider theme={theme}>
  - <Block color="bodytext">
  + <Box color="bodytext">
  <UnderlineNav
  actions={
  <Text color="gray.5" fontFamily="mono" px={4}>
  @@ -34,8 +34,8 @@ export default function Page({render}) {
  Sandbox
  </UnderlineNavLink>
  </UnderlineNav>
  - <Block p={3}>{render()}</Block>
  - </Block>
  + <Box p={3}>{render()}</Box>
  + </Box>
  </ThemeProvider>
  </React.Fragment>
  )
  