feat: reduce `apple-touch-icon` size

Trade off Hugo build time rather than re-use existing standard icon sizes.

wowchemy/layouts/partials/site_head.html

@@ -184,7 +184,7 @@
   {{ end }}
 
   <link rel="icon" type="image/png" href="{{(partial "functions/get_icon" 32).RelPermalink}}">
-  <link rel="apple-touch-icon" type="image/png" href="{{(partial "functions/get_icon" 192).RelPermalink}}">
+  <link rel="apple-touch-icon" type="image/png" href="{{(partial "functions/get_icon" 180).RelPermalink}}">
 
   <link rel="canonical" href="{{ .Permalink }}">