Refactor fireworks.js: clean up observer options for improved readability

Jellyfin.Plugin.Seasonals/Web/fireworks.js

@@ -60,9 +60,9 @@ const observer = new MutationObserver(toggleFirework);
 
 // start observation
 observer.observe(document.body, {
-  childList: true,    // observe adding/removing of child elements
+  childList: true,
-  subtree: true,      // observe all levels of the DOM tree
+  subtree: true,
-  attributes: true    // observe changes to attributes (e.g. class changes)
+  attributes: true 
 });