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/postcss/lib/document.js

@@ -0,0 +1,33 @@
+'use strict'
+
+let Container = require('./container')
+
+let LazyResult, Processor
+
+class Document extends Container {
+  constructor(defaults) {
+    // type needs to be passed to super, otherwise child roots won't be normalized correctly
+    super({ type: 'document', ...defaults })
+
+    if (!this.nodes) {
+      this.nodes = []
+    }
+  }
+
+  toResult(opts = {}) {
+    let lazy = new LazyResult(new Processor(), this, opts)
+
+    return lazy.stringify()
+  }
+}
+
+Document.registerLazyResult = dependant => {
+  LazyResult = dependant
+}
+
+Document.registerProcessor = dependant => {
+  Processor = dependant
+}
+
+module.exports = Document
+Document.default = Document