feat: Initial search implementation using pagefind.

Sources/Docs/Templates/BaseLayout.swift

@@ -127,6 +127,16 @@ private func generateHeader(_ pageTitle: String, _ extraHeader: NodeConvertible)
     link(href: "/static/style.css", rel: "stylesheet")
     link(href: "/articles/feed.xml", rel: "alternate", title: SiteMetadata.name, type: "application/rss+xml")
     extraHeader
-    script(src: "https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js")
+    // script(src: "https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js")
+    //
+    Node.raw("""
+    <script src="/pagefind/pagefind-ui.js"></script>
+    <link href="/pagefind/pagefind-ui.css" rel="stylesheet">
+    <script>
+        window.addEventListener('DOMContentLoaded', (event) => {
+            new PagefindUI({ element: "#search", showSubResults: true });
+        });
+    </script>
+    """)
   }
 }