chore: correct TS for mutations without extra code

[gmaclennan]

The mutation hooks currently do this:

	return status === 'error'
		? { error, mutate, reset, status }
		: { error: null, mutate, reset, status }

To force typescript into returning the correct distributive type.

This is a follow-up to this comment about better ways to do this.

This is one solution, implementing a pick function (similar to what the current object spread and object create is doing) that correctly maintains the types. Adds Simplify from type-fest so that the return types are more readable for the library consumer.

Leaving this here as an idea, not fully implemented, feel free to ignore or finish the implementation.