dfr uppercase for dataframe

Uppercase the strings in the column.

Signature

> dfr uppercase

Examples

Modifies strings to uppercase

> [Abc aBc abC] | dfr into-df | dfr uppercase
╭───┬─────╮
│ # │  0  │
├───┼─────┤
│ 0 │ ABC │
│ 1 │ ABC │
│ 2 │ ABC │
╰───┴─────╯