Move a bunch of shortcodes and partials back from the platters theme

layouts/shortcodes/img.html

@@ -0,0 +1,21 @@
+{{ $img := dict }}
+{{ with .Get "name" }}
+    {{ $img = $.Page.Resources.GetMatch . }}
+{{ else }}
+    {{ errorf "No name given to img shortcode" }}
+{{ end }}
+
+{{/* Space separated list of classes to apply to the <img> tag */}}
+{{ $classes := .Get "class" }}
+
+{{ $altText := .Get "alt" | default $img.Params.alt }}
+{{ if not $altText }}
+    {{ warnf "Image doesn't have alt text: %s" $img.RelPermalink }}
+{{ end }}
+
+{{ $resizedImg := $img.Fit "1280x1280" }}
+<img src="{{ $resizedImg.RelPermalink }}"
+     width="{{ $resizedImg.Width }}"
+     height="{{ $resizedImg.Height }}"
+     alt="{{ $altText }}"
+     {{ with $classes }}class="{{ . }}"{{ end }}>