add js for dynamic class for navbar

public/js/nav.js

@@ -0,0 +1,13 @@
+function applyHeaderShadow() {
+  const header = document.querySelector(".web-header-emit-shadow-when-top");
+  if (!header) return;
+
+  window.addEventListener("scroll", () => {
+    if (window.scrollY > 0) {
+      header.classList.add("shadow-active");
+    } else {
+      header.classList.remove("shadow-active");
+    }
+  });
+}
+document.addEventListener("DOMContentLoaded", applyHeaderShadow);