Initial commit: notification-elements-demo app

Interactive Angular 19 demo for @sda/notification-elements-ui with
6 sections: Bell & Feed, Notification Center, Inbox, Comments &
Threads, Mention Input, and Full-Featured layout. Includes mock
data, dark mode toggle, and real-time event log.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

node_modules/core-js-compat/index.js

@@ -0,0 +1,14 @@
+'use strict';
+const compat = require('./compat');
+const data = require('./data');
+const entries = require('./entries');
+const getModulesListForTargetVersion = require('./get-modules-list-for-target-version');
+const modules = require('./modules');
+
+module.exports = Object.assign(compat, {
+  compat,
+  data,
+  entries,
+  getModulesListForTargetVersion,
+  modules,
+});