refactor: migrate parsers to TS (#133)

* dev: finish top-level parsers TS migration

* dev: migrate menu renderers to TS

* chore: fix ts errors

* dev: finish ts migration 🎉

src/parser/classes/ExpandedShelfContents.ts

@@ -0,0 +1,20 @@
+import Parser from '../index';
+import { YTNode } from '../helpers';
+
+class ExpandedShelfContents extends YTNode {
+  static type = 'ExpandedShelfContents';
+
+  items;
+
+  constructor(data: any) {
+    super();
+    this.items = Parser.parse(data.items);
+  }
+
+  // XXX: alias for consistency
+  get contents() {
+    return this.items;
+  }
+}
+
+export default ExpandedShelfContents;