Add an optional callback to ColumnOptions to allow custom formatting at the column level

Summary

Add an optional callback function to the ColumnOptions object that can be used to perform custom formatting or additional processing of a specific columns.

Motivation

Of of the box csv-stringify only supports formatting by data type. This does not allow different formats for different types of columns. For example a column that contain dates as opposed to a column that is a date-time. The same situation occurs when you have a output that requires both numbers and currencies.

Alternative

I am currently constructing an array of functions that are applied in a ForEach() to the rows of the original input.

stringify(
          rows.map(row => {
            this.formatters?.forEach( fmt => fmt(row) );
            return row;
          }),
          {
            header: addHeader,
            columns: this.columns
          }
)

A working Sample is here:
https://stackblitz.com/edit/typescript-column-format-ks3cs3?file=report-utils/csv-utils.ts

Draft

stringify(
      testData,
      {
        header: true,
        columns: [
          {key:'strVal', header: 'String'},
          {key:'dVal', header: 'Date', (value) => { return value.LocaleDateString(); }},
          {key:'dtVal', header: 'Date Time', (value) => { return `${value.toLocaleDateString()} ${value.toLocaleTimeString()}` }},
          {key:'currVal', header: 'Currency', (value) => { return value.toFixed(2); }}
        ]
)

Additional context

Add any other context or screenshots about the feature request here.

Start by locating the ColumnOptions definition and the stringify entry point used by the columns option. Review the StackBlitz example and existing column-formatting behavior, then determine the callback API and add coverage showing per-column formatting for dates and currencies.