message: Added Scrollablearea and buttons
diff: -<h2>{{course.name}}</h2>
  +<h1>{{course.name}}</h1>
  <ng-container *ngIf="!course.lectures.length">No lectures to download!</ng-container>
  +<mat-dialog-content>
  <mat-list *ngFor=" let lecture of course.lectures">
  <mat-list-item class="lecture">{{lecture.name}}</mat-list-item>
  <mat-list *ngFor=" let unit of lecture.units">
  <mat-list-item class = "unit">{{unit.name}}</mat-list-item>
  </mat-list>
  </mat-list>
  +</mat-dialog-content>
  +<mat-dialog-actions>
  + <button mat-button mat-dialog-close>No</button>
  + <button mat-button [mat-dialog-close]="true">Yes</button>
  +</mat-dialog-actions>
  