toCurrency method
Implementation
String toCurrency() {
final value = double.tryParse(this) ?? 0.0;
return "R\$ ${value.toStringAsFixed(2).replaceAll('.', ',')}"
.replaceAllMapped(RegExp(r'(\d{1,3})(?=(\d{3})+(?!\d))'), (Match m) => '${m[1]}.');
}