Add code block syntax highlighting to SPRAG docs

Author: BleedingXiko

docs/app/shell.css

@@ -950,6 +950,12 @@ details[open] > .sidebar-section-header::after {
   border: none;
 }
 
+.prose pre code.hljs {
+  overflow: visible;
+  padding: 0;
+  background: transparent;
+}
+
 .prose blockquote {
   margin: 1.25rem 0;
   padding: 0.85rem 1.15rem;

docs/app/shell.html

@@ -21,4 +21,11 @@
   <main class="page">
     {{ sprag_slot }}
   </main>
+  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.11.1/styles/github-dark.min.css">
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.11.1/highlight.min.js"></script>
+  <script>
+    if (window.hljs) {
+      window.hljs.highlightAll();
+    }
+  </script>
 </div>