Angular Material MatSelect:如何显示选项列表中未包含的选项？

<mat-form-field>
  <mat-label>选择选项</mat-label>
  <mat-select [(value)]="selectedOption">
    <mat-option *ngFor="let option of options" [value]="option">{{ option }}</mat-option>
    <mat-option (click)="showCustomOption()">其他</mat-option>
  </mat-select>
</mat-form-field>

<div *ngIf="showCustomInput">
  <mat-form-field>
    <input matInput placeholder="自定义选项" [(ngModel)]="customOption">
  </mat-form-field>
</div>