Goal: Implement the built-in `Readonly<T>` generic without using it. Constructs a type with all properties of `T` set to `readonly`, meaning the properties of the constructed type cannot be reassigned. For example: Source challenge: https://github.com/type-challenges/type-challenges/tree/main/questions/00007-easy-readonly Reference explanation: https://github.com/ghaiklor/type-challenges-solutions/blob/main/en/easy-readonly.md