RefRW<T> The component.
Gets a reference to the singleton component, for read/write access.
NOTE: this reference refers directly to the singleton's component memory.
Structural changes to the chunk where the singleton resides can invalidate this reference
and result in crashes or undefined behaviour if the reference is used after structural changes.
Additional resources: ComponentSystemBase.GetSingleton, EntityQuery.GetSingleton, EntityQuery.GetSingletonRW