Update tab.js

For test:
http://127.0.0.1:8000/activities#active=tab-invitationer
http://127.0.0.1:8000/activities#active=tab-aktiviteter
http://127.0.0.1:8000/activities#active=tab-tilmeldte-aktiviteter

members/static/members/js/tab.js

@@ -9,13 +9,23 @@ document.addEventListener("DOMContentLoaded", function(event) {
       Array.from(tabs.children).filter(element => element.tagName === "SECTION")
     );
 
+    // Get the 'active' parameter value from the URL fragment
+    const urlFragment = window.location.hash.substr(1); // Remove the '#' symbol
+    const activeItemId = urlFragment.split("=")[1];
+
+    // Default to the first list item as active if the ID is not provided or doesn't match any item
+    const activeIndex = tabButtons.findIndex(button => button.id === activeItemId);
+    const defaultIndex = activeIndex !== -1 ? activeIndex : 0;
+
     // Default to first as active
-    toggleActive(sections, tabButtons, 0);
+    toggleActive(sections, tabButtons, defaultIndex);
 
     for (var button of tabButtons) {
       button.addEventListener("click", event =>
         toggleActive(sections, tabButtons, tabButtons.indexOf(event.srcElement))
       );
+      const newUrl = window.location.pathname; // Remove any query parameters or hash from the URL
+      window.history.pushState({}, "", newUrl);
     }
   }
 });