Allows mapping through each csv row.

[emmsdan]

This PR will allow users to map through individual row, similar to [].map().

eg:

    const data = csvToJson
      .fieldDelimiter(",")
      .map((headers: string[], value: {Amount: number}, index) => {
        return {
           header: headers[1]
          ...value,
          ...priceConfiguration(value.Amount + 1),
        };
      })
     .getJsonFromCsv('some-csv-file.csv');

[iuccio]

@emmsdan Can you add some unit tests please? 🙏