message: Replace button with LinkButton in 404 page.
diff: import { useTranslation } from 'next-i18next'
  -import { useRouter } from 'next/router'
  -import { Button, Grid, Typography } from '@material-ui/core'
  +import { Grid, Typography } from '@material-ui/core'
  import { createStyles, Theme, makeStyles } from '@material-ui/core/styles'
  import ArrowBackIcon from '@material-ui/icons/ArrowBack'
  +import LinkButton from 'components/common/LinkButton'
  import Layout from 'components/layout/Layout'
  +import { routes } from 'common/routes'
  +
  import NotFoundIllustration from './assets/NotFoundIllustration'
  const useStyles = makeStyles((theme: Theme) =>
  @@ -21,8 +23,6 @@ const useStyles = makeStyles((theme: Theme) =>
  export default function NotFoundPage() {
  const { t } = useTranslation()
  - const router = useRouter()
  -
  const classes = useStyles()
  return (
  @@ -36,13 +36,14 @@ export default function NotFoundPage() {
  <Typography variant="body2">{t('errors:404Message')}</Typography>
  </Grid>
  <Grid container item alignItems="center" justify="center">
  - <Button
  + <LinkButton
  size="large"
  startIcon={<ArrowBackIcon />}
  + color="default"
  variant="outlined"
  - onClick={() => router.replace('/')}>
  + href={routes.index}>
  {t('errors:backButtonLabel')}
  - </Button>
  + </LinkButton>
  </Grid>
  </Grid>
  </Grid>
  