Goal: Implement the type version of `Array.lastIndexOf`. `LastIndexOf<T, U>` takes an Array `T`, any `U` and returns the index of the last `U` in Array `T`. For example: Source challenge: https://github.com/type-challenges/type-challenges/tree/main/questions/05317-medium-lastindexof Reference explanation: https://github.com/ghaiklor/type-challenges-solutions/blob/main/en/medium-lastindexof.md