outsource gallery part to separate partial

layouts/partials/gallery.html

@@ -0,0 +1,9 @@
+{{ $imgs := .imgs }}
+{{ $galno := .galno }}
+<div class="snap-gallery-wrapper" style="--columns:{{ default 4 .columns }};--min-width:{{ default 200 .minwidth }};">
+  {{ range $i, $img := $imgs }}
+  <div class="snap-image">
+    <img src="{{ $img }}" onclick="openModal({{ $galno }});currentSlide({{ $galno }}, {{ add $i 1 }});">
+  </div>
+  {{ end }}
+</div>