listenChooseLevelButton method

void listenChooseLevelButton ()

Listens to the 'choose level button' click events and shows the 'chooseLevelsView'

Implementation 

void listenChooseLevelButton() {
  querySelector("#button_choose_levels").onClick.listen((MouseEvent e) {
    this.showChooseLevelsView(this._nrAvailableLevels, this.getReachedLevel());
  });
}