Add noreferrer to image tags

This doesn't cover the magical div ones, but it's a start

layouts/_default/_markup/render-image.html

@@ -8,7 +8,7 @@
 
 <figure class="text-center">
   <a href="{{ $destination | safeURL }}" target="_blank">
-    <img src="{{ $destination | safeURL }}" alt="{{ .Text | plainify }}" style='max-width: {{ default "90" .Title }}%;'/>
+    <img src="{{ $destination | safeURL }}" alt="{{ .Text | plainify }}" style='max-width: {{ default "90" .Title }}%;' referrerpolicy="no-referrer"/>
   </a>
   <figcaption class="text-center">
     <small>{{ .Text | markdownify }}</small>

layouts/_default/flickr.html

@@ -12,7 +12,7 @@
     <div id="light-gallery" class="row">
     {{ range $element := $photoset.photo }}
       <a href="{{ $element.url_k }}" title="{{ $element.title }}" class="col-md-2 col-xs-12">
-        <img src="{{ $element.url_q }}" alt="{{ $element.title }}"/>
+        <img src="{{ $element.url_q }}" alt="{{ $element.title }}" referrerpolicy="no-referrer"/>
       </a>
     {{ end }}
     </div>

layouts/shortcodes/mermaid.html

@@ -3,7 +3,7 @@
 {{ $data := dict "code" .Inner "mermaid" $mermaidData }}
 
 <figure class="mermaid">
-  <img src="https://mermaid.ink/img/{{ $data | jsonify | base64Encode }}" />
+  <img src="https://mermaid.ink/img/{{ $data | jsonify | base64Encode }}" referrerpolicy="no-referrer" />
   <figcaption class="text-center">
     <small>{{ .Get "caption" }}</small>
   </figcaption>