layouts/images: allow opt-out from lightbox

Authors can now pass `lightbox=false` as a query parameter with their
image URL to disable the lightbox effect; this is especially useful for
smaller images that do not have a lot of detail.

Signed-off-by: Luca Zeuch <[email protected]>

Author: l-zeuch

layouts/_default/_markup/render-image.html

@@ -109,6 +109,11 @@
 {{- end }}
 
 {{- $lightbox := true }}
+{{- if $u.RawQuery }}
+  {{- if $u.Query.Has "lightbox" }}
+    {{- $lightbox = ne ($u.Query.Get "lightbox") "false" }}
+  {{- end }}
+{{- end }}
 
 {{- /* Render image element. */ -}}
 {{- if $lightbox -}}