add functionality to delete employee button (#11)

Reviewed-on: #11
Reviewed-by: Hernd Beidemann <huydw@proton.me>

src/app/employee-list/employee-list.component.html

@@ -37,7 +37,7 @@
                   <button mat-icon-button color="primary" [matTooltip]="'Edit employee'" class="!mr-2">
                     <mat-icon>edit</mat-icon>
                   </button>
-                  <button mat-icon-button color="warn" [matTooltip]="'Delete employee'">
+                  <button mat-icon-button color="warn" [matTooltip]="'Delete employee'" (click)="openDeleteDialogue(employee)">
                     <mat-icon>delete</mat-icon>
                   </button>
                 </td>