listenDonateButton method

void listenDonateButton ()

Listens to the 'donate button' click events and opens a new window directing to paypal

Implementation 

void listenDonateButton() {
  querySelector("#donate-button").onClick.listen((MouseEvent e) {
    window.open("https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=EW22STTHR8DK2&source=url",
        "Donate on PayPal");
  });
}