basic code highlighting for our docs

src/site/_plugins/prettify.rb

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 require 'cgi'
 
 module Prettify
 
   # Wraps code with tags for Prettify.
   #
@@ skipping 13 matching lines @@
       if markup =~ Syntax
         @lang = $1
       end
     end
 
     def render(context)
       out = '<pre class="prettyprint'
       unless @lang.nil?
         out += ' lang-' + @lang
       end
-      out += '">' + CGI::escapeHTML(super) + "</pre>"
+      out += '">'
+
+      contents = super.strip
+      contents = CGI::escapeHTML(contents)
+      contents.gsub!('[[highlight]]', '<code class="nocode highlight">')
+      contents.gsub!('[[/highlight]]', '</code>')
+
+      out += contents + "</pre>"
     end
 
   end
 end
 
 Liquid::Template.register_tag('prettify', Prettify::Tag)