move css minification from postcss to webpack (for better source maps)

layouts/partials/functions/init.html

@@ -10,7 +10,7 @@
   {{- with .Params.css -}}
     {{/* NOTE: This file doesn't end up getting published (which is good) */}}
     {{- $target := path.Join $.File.Dir "css/inline.scss" -}}
-    {{- $css := . | resources.FromString $target | resources.PostCSS (dict "config" "postcss.config.js") -}}
+    {{- $css := . | resources.FromString $target -}}
 <style>
 {{ $css.Content | safeCSS }}
 </style>