Fix ValidatorFunc Type Mistake

[foolishflyfox]

The ValidatorFunc defined in Factory.ts has a mistake.

For Example:

addGetterSetter<T extends Constructor, U extends Attr<T>>(
    constructor: T,
    attr: U,
    def?: Value<T, U>,
    validator?: ValidatorFunc<Value<T, U>>,
    after?: AfterFunc<T>
)

because Value<T, U> has do ExtractGetSet ：

type Value<T extends Constructor, U extends Attr<T>> = ExtractGetSet<InstanceType<T>[U]>

but ValidatorFunc do ExtractGetSet again:

type ValidatorFunc<T> = (val: ExtractGetSet<T>, attr: string) => T;

so, the val is always never, and with VSCode can see this phenomenon：

my change can fix this mistake:

[lavrton]

Well, in validator, val should be any. never is not correct. And in that example number is not correct as well, because validator should check any value.