QOL for InstanceFinder registerable instances

[celojevic]

InstanceFinder.RegisterInstance is a great and easy replacement for singletons but it is missing some QOL. One thing its missing so far is that you cant check if the instance already exists with like InstanceFinder.HasInstance<Type>. You can do InstanceFinder.GetInstance<Type>() != null but there is no option to turn the warning off if the instance is not found

[FirstGearGames]

I can do that and add optional for warning(probably).

Don't forget there is also this ... RegisterInvokeOnInstance<T>

[FirstGearGames]

Apparently there is a warn option ... but I may have added it in after this conversion.
public T GetInstance<T>(bool warn = true) where T : UnityComponent

[FirstGearGames]

Added in 3.5.3