Function spsheet::index_to_column

pub fn index_to_column(index: usize) -> String

Usize index to String index

use spsheet::*;
assert_eq!("A", index_to_column(0));
assert_eq!("B", index_to_column(1));
assert_eq!("Z", index_to_column(25));
assert_eq!("AA", index_to_column(26));