Merge branch 'poc-diagrams-extra'

Another fixup was necessary, to support the cheat sheet (which is not
a regular page but an `_index` one, i.e. a `list`, which is a "special
page" in Hugo parlance).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

layouts/diagram-list.html

@@ -1,7 +1,7 @@
 <pre>
-{{- range .Site.RegularPages -}}
+{{ range .Site.Pages -}}
   {{- if in .RawContent "{{< graphviz" -}}
-    public{{ .Path }}.html
-  {{- end }}
-{{ end -}}
+     public{{ .Path }}.html{{ "\n" -}}
+  {{- end -}}
+{{- end -}}
 </pre>