feat(es_extended): Extra callback functions

[Mycroft-Studios]

Introduces 2 new functions:
ESX.DoesClientCallbackExist
ESX.DoesServerCallbackExist

[Kenshiin13]

I don't see the point of this. ESX already throws an error if a resource attempts to access an invalid callback. This just promotes people calling ESX.DoesServerCallbackExist and ESX.DoesClientCallbackExist before every damn callback.

Third party resources can check if their dependencies are started and just assume that all expected callbacks are registered. We are already letting them know if they are not ^^

[Arctos2win]

I don't see the point of this. ESX already throws an error if a resource attempts to access an invalid callback. This just promotes people calling ESX.DoesServerCallbackExist and ESX.DoesClientCallbackExist before every damn callback.

Third party resources can check if their dependencies are started and just assume that all expected callbacks are registered. We are already letting them know if they are not ^^

I agree with Kenshin on this one, there is 0 usecase for it and litterly no one ever requested a functionality like this
in the so many years this project exists.

[Kenshiin13]

@Mycroft-Studios

[Kenshiin13]

LGTM!