add click events to date time ionic code example

Example: ionic button trigger ion-datetime

<button ion-button icon-right (click)="picker.open()">
    <ion-datetime #picker pickerFormat="DD MMMM YYYY" [min]="datePickerMin" [(ngModel)]="datePicker" (ionChange)="changeDate()"></ion-datetime>
    <ion-icon name="calendar"></ion-icon>
</button>