{{ range $header, $projects := . }}
<article class="projects">
  <h2 class="projects_header section-header">{{ $header }}</h2>
  {{ range $projects }}
  <article class="project">
    <h2 class="project__title">{{ .title | safeHTML }}</h2>
    <p class="project__content">{{ .content | safeHTML }}</p>
  </article>
  {{ end }}
</article>
{{ end }}