feat: inject highlight_styles inline style block into web.html head section

src/snek/templates/web.html

@@ -4,6 +4,7 @@
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>Snek</title>
+  <style>{{highlight_styles}}</style>
   <script src="/media-upload.js"></script>
   <script src="/html-frame.js"></script>
   <script src="/schedule.js"></script>
@@ -59,4 +60,4 @@ let installPrompt = null
         ;
     </script>
 </body>
-</html>
+</html>