feat: add music#getRecap() (#165)

* dev: add recap renderer parsers

* dev: finish implementation ✨

* docs: update YouTube Music API ref

src/parser/classes/MusicElementHeader.ts

@@ -0,0 +1,17 @@
+import Parser from '../index';
+import Element from './Element';
+
+import { YTNode } from '../helpers';
+
+class MusicElementHeader extends YTNode {
+  static type = 'MusicElementHeader';
+
+  element: Element | null;
+
+  constructor(data: any) {
+    super();
+    this.element = Reflect.has(data, 'elementRenderer') ? Parser.parseItem<Element>(data, Element) : null;
+  }
+}
+
+export default MusicElementHeader;