Replaces the use of jQuery with plain JavaScript.

Closes #3502585

css/sitestudio_extras.autocomplete.css

+/* Base styles for the autocomplete list */
+.sitestudio-extras-autocomplete-list {
+  position: absolute;
+  background-color: #fff;
+  border-radius: 4px;
+  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
+  max-height: 200px;
+  overflow-y: auto;
+  padding: 0;
+  margin: 0;
+  list-style: none;
+  z-index: 1000;
+  display: block;
+}
+
+/* Style for each list item */
+.sitestudio-extras-autocomplete-list li {
+  padding: 8px 12px;
+  cursor: pointer;
+  font-size: 14px;
+  color: #333;
+}
+
+/* Highlight item on hover */
+.sitestudio-extras-autocomplete-list li:hover {
+  background-color: #f0f0f0;
+}
+
+/* Style for "No Results" message */
+.sitestudio-extras-autocomplete-list .no-result {
+  font-style: italic;
+  color: #999;
+  text-align: center;
+  padding: 10px;
+}
+
+/* Add a scrollbar for overflow */
+.sitestudio-extras-autocomplete-list::-webkit-scrollbar {
+  width: 6px;
+}
+
+.sitestudio-extras-autocomplete-list::-webkit-scrollbar-thumb {
+  background-color: #ccc;
+  border-radius: 4px;
+}
+
+.sitestudio-extras-autocomplete-list::-webkit-scrollbar-thumb:hover {
+  background-color: #aaa;
+}