[Post-7.0] Improve readability of `Array.from` / `TypedArray.from` `mapFn` parameters

Currently, the mapFn argument of Array.from() is typed as (v: T, k: number) => U.
However, when this information is displayed in an IDE tooltip, it is difficult to grasp what values are passed to v and k.

To improve clarity, I propose changing the type definition to (element: T, index: number) => U, following the description of the same method in MDN Web Docs. The same applies to TypedArray.from().

Supplementary Information:

• The target file is internal/bundled/libs/lib.es2015.iterable.d.ts#L107.
• These changes are not intended to fix differences between 6.0 and 7.0, and according to CONTRIBUTING.md, the Pull Request should be submitted after the 7.0 release. I plan to submit a Pull Request for this once 7.0 is released.

Comienza en internal/bundled/libs/lib.es2015.iterable.d.ts#L107 y localiza las declaraciones de mapFn de Array.from y TypedArray.from. Compara los nombres de sus parámetros con la descripción vinculada de MDN y confirma después que ambas declaraciones usan nombres descriptivos para el elemento y el índice sin cambiar sus tipos ni su comportamiento.