feat(ytmusic): music#Playlist fixes and additions (#138)

* feat: add MusicEditablePlaylistDetailHeader parser

* feat: more info in `DropdownItem`

* fix: empty `year` value in `MusicDetailHeader`

* fix(ytmusic#Playlist): header err w/ own playlists

* feat: include reload continuation in `MusicShelf`

* feat(ytmusic): add getSuggestions() to Playlist

src/parser/classes/MusicEditablePlaylistDetailHeader.ts

@@ -0,0 +1,18 @@
+import Parser from '../index';
+import { YTNode } from '../helpers';
+
+class MusicEditablePlaylistDetailHeader extends YTNode {
+  static type = 'MusicEditablePlaylistDetailHeader';
+
+  header;
+
+  constructor(data: any) {
+    super();
+    this.header = Parser.parse(data.header);
+
+    // TODO: Should we also parse data.editHeader.musicPlaylistEditHeaderRenderer?
+    // It doesn't seem practical to do so...
+  }
+}
+
+export default MusicEditablePlaylistDetailHeader;