feat: add support for topic/auto-generated channels and fix minor parsing errors (#233)

* dev: add support for topic channels

* dev(parser): do not try to parse empty nodes

* dev: add support for auto-generated game channels

src/parser/classes/PlaylistCustomThumbnail.ts

@@ -0,0 +1,13 @@
+import { YTNode } from '../helpers';
+import Thumbnail from './misc/Thumbnail';
+
+export default class PlaylistCustomThumbnail extends YTNode {
+  static type = 'PlaylistCustomThumbnail';
+
+  thumbnail: Thumbnail[];
+
+  constructor(data: any) {
+    super();
+    this.thumbnail = Thumbnail.fromResponse(data.thumbnail);
+  }
+}