Fix toString(style:) for .month, .shortMonth and .veryShortMonth

[j0sm3n]

When converting Date to String using predefined month styles, the function is returning incorrect values.

let date = Date() // 26/3/2024

date.toString(style: .month) // April
date.toString(style: .shortMonth) // Apr
date.toString(style: .veryShortMonth) // A

I fixed it with .toString(format: .custom(String)) for each case.