Implemented phase 1 for the POC prototype in the Website service.

Services/Website/Resources/Static/js/shared.js

@@ -0,0 +1,23 @@
+// CCN — shared script. Every screen works without it; it only removes a click here and there.
+
+document.documentElement.classList.add("js");
+
+// Selects marked `data-autosubmit` submit their form on change.
+for (const select of document.querySelectorAll("select[data-autosubmit]")) {
+  select.addEventListener("change", () => select.form?.requestSubmit());
+}
+
+// The filter rail is a disclosure, open on desktop. Browsers without `::details-content` need it opened here.
+const filters = document.querySelector("details.filters");
+const desktop = window.matchMedia("(min-width: 1024px)");
+
+if (filters) {
+  const sync = () => {
+    if (desktop.matches) {
+      filters.open = true;
+    }
+  };
+
+  sync();
+  desktop.addEventListener("change", sync);
+}