Add useRefs hook

[rimuy]

Proposed changes

As your game UI grows, it becomes really difficult to track the instances you want to filter the references - If I had a tree of functions that returns instances, and want to capture one of its descendants, I'd have to pass my ref table all the way down the tree just so I could set the reference to be that one instance.

The proposed new hook called useRefs, eliminates this issue by grabbing the ref table in the current useInstance call. This can only be used inside useInstance and will error if done otherwise.

Additional comments

• Adds the missing parameter type for useInstance's callback.
• Freezes the ref table after useCallback is done executing as it shouldn't be mutated anyways. (New hook's behavior also depends on this)

[Ukendio]

It needs some tests, primarily because it is new and unproven API but also want to see examples of how it would be used in several scenarios.

[LastTalon]

Could you link this to an issue to discuss the actual use case of this hook?