Load serialized objects asynchronously

Prefabs and other serialized content can be loaded in asynchronously via Resources.LoadAsync(), which will offload reading from disk onto a worker thread that eases the burden on the main thread. It will take some time for the serialized object to become available, which can be checked by calling the isDone property on the ResourceRequest object returned by the previous method call.

This is not ideal for Prefabs we need immediately at the start of the game, but all future Prefabs are good candidates for asynchronous loading if we're willing to create systems that manage this behaviour.