currencyPair function
Return a list of two currencies, where the second currency is not the same as the first currency.
Returns: A list of two currencies.
Implementation
List<Currency> currencyPair() {
/// creating a varible using the `currency` function from
/// the `currency.dart` file.
final currency1 = currency();
/// Calling the `currency` function from the `currency.dart` file,
/// but passing in a parameter to
/// remove the first currency from the list of currencies.
final currency2 = currency(currencyKeyToRemove: currency1.code);
return [currency1, currency2];
}