Expose rollbacks to the API, refactor the scheduler

proxy/src/main/java/dev/plex/api/impl/DefaultPlexApi.java

@@ -12,6 +12,7 @@ import dev.plex.api.message.MessageApi;
 import dev.plex.api.module.ModulesApi;
 import dev.plex.api.player.PlayersApi;
 import dev.plex.api.punishment.PunishmentsApi;
+import dev.plex.api.rollback.RollbackApi;
 import dev.plex.api.scheduler.SchedulerApi;
 import dev.plex.api.storage.StorageApi;
 
@@ -38,6 +39,7 @@ public final class DefaultPlexApi implements PlexApi
     @Override public MessageApi messages() { throw unsupported(); }
     @Override public PlayersApi players() { throw unsupported(); }
     @Override public PunishmentsApi punishments() { throw unsupported(); }
+    @Override public RollbackApi rollback() { throw unsupported(); }
     @Override public SchedulerApi scheduler() { throw unsupported(); }
     @Override public StorageApi storage() { throw unsupported(); }