fix: incorrect node parser implementations (#428)

These were causing some issues in v5.2.0.

src/parser/classes/EngagementPanelTitleHeader.ts

@@ -0,0 +1,17 @@
+import { YTNode } from '../helpers.js';
+import { Parser, type RawNode } from '../index.js';
+import Text from './misc/Text.js';
+import Button from './Button.js';
+
+export default class EngagementPanelTitleHeader extends YTNode {
+  static type = 'EngagementPanelTitleHeader';
+
+  title: Text;
+  visibility_button: Button | null;
+
+  constructor(data: RawNode) {
+    super();
+    this.title = new Text(data.title);
+    this.visibility_button = Parser.parseItem(data.visibilityButton, Button);
+  }
+}