0.53 now with unity security fix and cloud save

We've added Steam Cloud saves to the game in this version! Since this functionality can be a bit finicky in terms of keeping tabs on which data is the most recent, we've added some redundancy to ensure that things consistently work as intended.

The game should also start up faster than before (both in reaching the title screen and song select).

This version also contains a required security update for all games made with Unity.