add UI to show assigned user

frontend/allowance-planner-v2/src/app/pages/tasks/tasks.page.html

@@ -19,6 +19,7 @@
         <button (click)="completeTask(task.id)">Done</button>
         <div (click)="updateTask(task.id)" class="item">
           <div class="name">{{ task.name }}</div>
+          <div class="assigned">{{ usernames[task.assigned ? task.assigned : 0] }}</div>
           <div
             class="reward"
             [ngClass]="{ 'negative': task.reward < 0 }"