Fix spawn event handler comment and plan to port to async event

Author: NonSwag

src/main/java/net/thenextlvl/tweaks/listener/SpawnListener.java

@@ -17,6 +17,7 @@ public SpawnListener(TweaksPlugin plugin) {
         this.plugin = plugin;
     }
 
+    // todo: port to AsyncPlayerSpawnLocationEvent
     @EventHandler(priority = EventPriority.LOWEST)
     public void onPlayerSpawnLocation(PlayerSpawnLocationEvent event) {
         var config = plugin.config().spawn;