Add activity.js, infinite scroll for notifications

resources/assets/js/activity.js

@@ -0,0 +1,10 @@
+$(document).ready(function() {
+  $('.pagination').hide();
+  let elem = document.querySelector('.notification-page .list-group');
+  let infScroll = new InfiniteScroll( elem, {
+    path: '.pagination__next',
+    append: '.notification-page .list-group',
+    status: '.page-load-status',
+    history: true,
+  });
+});