style: start using SASS and assets

* NEW Adds assets/scss directories.
* Copies static/styles.css to assets/scss/main.scss
* Improves head layouts to compile assets depending if on server or
  build.

Co-Authored-by: Igor Milhit <igor@milhit.ch>

layouts/partials/head.html

@@ -3,7 +3,16 @@
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>{{ .Title  }} | {{ .Site.Title }}</title>
 	<link rel="canonical" href="{{ .Permalink  }}">
-  <link rel="stylesheet" type="text/css" href="{{ .Site.BaseURL }}style.css">
+  {{ if .Site.IsServer }}
+    {{ $options := (dict "targetPath" "styles.css" "enableSourceMap" true) }}
+    {{ $styles := resources.Get "scss/main.scss" | toCSS $options }}
+    <link rel="stylesheet" href="{{ $styles.Permalink }}" media="screen">
+  {{ else }}
+    {{ $options := (dict "targetPath" "styles.css") }}
+    {{ $styles := resources.Get "scss/main.scss" | toCSS $options | minify }}
+    <link rel="stylesheet" href="{{ $styles.Permalink }}" media="screen">
+  {{ end }}
+  <!-- <link rel="stylesheet" type="text/css" href="{{ .Site.BaseURL }}style.css"> -->
   {{ with .OutputFormats.Get "RSS" }}
     {{ printf `<link rel="%s" type="%s" href="%s" title="%s" />` .Rel .MediaType.Type .Permalink $.Site.Title | safeHTML }}
   {{ end }}