message: Add noindex in dev mode.
diff: <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  + {{ if .Site.Params.devMode }}
  + <meta name="robots" content="noindex" />
  + {{ end }}
  <title>
  {{- block "title" . -}}
  