Add sticky header feature

sticky-header/steacky-header.js

@@ -0,0 +1,20 @@
+const HEADER_POINT = 70;
+let lastScrollY = window.scrollY;
+
+window.addEventListener("scroll", () => {
+  if (app_shop.vars.view === 1 || app_shop.vars.view === 2) return;
+
+  const container = document.querySelector("#container");
+  if (container.classList.contains("projector_page")) return;
+
+  const bodyEl = document.querySelector("body");
+  const currentScroll = window.scrollY;
+
+  if (currentScroll < lastScrollY && currentScroll > HEADER_POINT) {
+    bodyEl.classList.add("desktop-menu__scroll");
+  } else {
+    bodyEl.classList.remove("desktop-menu__scroll");
+  }
+  
+  lastScrollY = currentScroll;
+});