refactor: clean up, fix & remove outdated code (#228)

* dev: refactor and remove redundant code

* docs(music): update `Library` API ref

* docs: update examples

* chore: update lock file

src/parser/classes/MusicSideAlignedItem.ts

@@ -6,6 +6,7 @@ class MusicSideAlignedItem extends YTNode {
   static type = 'MusicSideAlignedItem';
 
   start_items?;
+  end_items?;
 
   constructor(data: any) {
     super();
@@ -13,6 +14,10 @@ class MusicSideAlignedItem extends YTNode {
     if (data.startItems) {
       this.start_items = Parser.parseArray(data.startItems);
     }
+
+    if (data.endItems) {
+      this.end_items = Parser.parseArray(data.endItems);
+    }
   }
 }