docs: fix demo source link
docs: fix demo source link

juanfc/angular-calendar,juanfc/angular-calendar,mattlewis92/angular-calendar,juanfc/angular-calendar,SamindaK/angular-calendar,mattlewis92/angular-calendar,mattlewis92/angular-calendar,SamindaK/angular-calendar,mattlewis92/angular2-calendar,mattlewis92/angular2-calendar,mattlewis92/angular-calendar,mattlewis92/angular2-calendar,SamindaK/angular-calendar,juanfc/angular-calendar