added ability to specify card 'status'

[darki73]

This pull request adds an ability to specify the 'status' of the card, similar to this:

(this image was obtained by googling "mastercard platinum")

When:

return CreditCardWidget(
  bankName: 'ADCB',
  cardStatus: 'Platinum',
);

When:

return CreditCardWidget(
  bankName: 'ADCB',
);

When:

return CreditCardWidget(
  cardStatus: 'Platinum',
);

[darki73]

I know I'm using too many if conditions, but this PR was hastily thrown together during the development of my application.