Use styles for syntax highlighting in XML

layouts/_default/_markup/render-codeblock.atom.xml

@@ -1,3 +1,14 @@
-{{ $result := transform.HighlightCodeBlock . (merge .Options (dict "noclasses" true "style" "github")) }}
+{{ $context := . }}
+
+{{ $options := dict }}
+{{ $overrides := dict "noclasses" true }}
+
+{{ with $context.Options }}
+    {{ $options = merge $overrides . }}
+{{ else }}
+    {{ $options = $overrides }}
+{{ end }}
+
+{{ $result := transform.HighlightCodeBlock $context $options }}
 
 {{ $result.Wrapped }}

layouts/_default/_markup/render-codeblock.rss.xml

@@ -1,3 +1,14 @@
-{{ $result := transform.HighlightCodeBlock . (merge .Options (dict "noclasses" true "style" "github")) }}
+{{ $context := . }}
+
+{{ $options := dict }}
+{{ $overrides := dict "noclasses" true }}
+
+{{ with $context.Options }}
+    {{ $options = merge $overrides . }}
+{{ else }}
+    {{ $options = $overrides }}
+{{ end }}
+
+{{ $result := transform.HighlightCodeBlock $context $options }}
 
 {{ $result.Wrapped }}

layouts/shortcodes/paige/code.xml

@@ -0,0 +1,20 @@
+{{ $content := .InnerDeindent | strings.TrimLeft "\f\n\r\v" | strings.TrimRight "\f\n\r\t\v " }}
+{{ $lang := .Get 0 | default (.Get "lang") | default "plaintext" }}
+{{ $options := .Get "options" }}
+{{ $unescape := .Get "unescape" }}
+
+{{ if not $content }}
+    {{ errorf "layouts/shortcodes/paige/code.xml: no content" }}
+{{ end }}
+
+{{ if $options }}
+    {{ $options = printf "%s,noclasses=true" $options }}
+{{ else }}
+    {{ $options = "noclasses=true" }}
+{{ end }}
+
+{{ if $unescape }}
+    {{ $content = htmlUnescape $content }}
+{{ end }}
+
+<div class="paige-shortcode-code">{{ highlight $content $lang $options }}</div>