{{ $JSON := $.Site.Data.principles }}
{{ $included := split (.Get "include") ", " }}
<ul>
  {{ range $JSON.principles }}
    {{ $title := lower .title }}
    {{ if in $included $title }}
      <li>
        <strong><a href="https://inclusivedesignprinciples.org#{{ .title | urlize }}">{{ .title }}</a>:</strong> {{ .strapline }}
      </li>
    {{ end }}
  {{ end }}
</ul>