message: Adding markdown body to the doc body
diff: @@ -3,6 +3,7 @@ import App, {Container} from 'next/app'
  import {Layout} from 'mdx-docs'
  import Octicon, {iconsByName} from '@githubprimer/octicons-react'
  import * as primerComponents from '../src'
  +import {Box, FlexContainer} from '../src'
  import * as docComponents from './doc-components'
  import SideNav from './doc-components/SideNav'
  import Header from './doc-components/Header'
  @@ -36,7 +37,9 @@ export default class MyApp extends App {
  <Header />
  <FlexContainer>
  <SideNav/>
  + <Box maxWidth={1012} my={6} mx={'auto'} px={6} className="markdown-body">
  <Component {...page} />
  + </Box>
  </FlexContainer>
  </Layout>
  </Container>
  