add grepper extension code example

Example 1: grepper chrome extension

Install grepper at: https://chrome.google.com/webstore/detail/grepper/amaaokahonnfjjemodnpmeenfpnnbkco

Example 2: add grepper

Ng If and Ng For use together for Ion Select
    <ion-item>
      <ion-label>Member Name 会员名字</ion-label>
      <ion-select [(ngModel)]="invoice.membername"  placeholder="Select One">
        <ng-container *ngFor="let c of members">
        <ion-select-option  *ngIf="c.by == userid" [value]="c.name">
          {{ c.name }}
        </ion-select-option>
      </ng-container>
      </ion-select>
    </ion-item>