Make help- and imprint-page accessible by tabulator, first try at cookie page

src/app/components/home/_dialogs/imprint/imprint.component.html

@@ -20,5 +20,4 @@
   <div class="visually-hidden">
     <div id="close-label">{{ 'imprint.close-label'| translate }}</div>
   </div>
-
 </div>

src/app/components/shared/_dialogs/help-page/help-page.component.html

@@ -3,10 +3,10 @@
   <h1 tabindex="0" class="modal" mat-dialog-title>{{ 'help.title' | translate }} </h1>
 
   <mat-divider></mat-divider>
-  <div tabindex="0">
+  <mat-dialog-content tabindex="0">
     <app-help-en *ngIf="currentLang=='en'"></app-help-en>
     <app-help-de *ngIf="currentLang=='de'"></app-help-de>
-  </div>
+  </mat-dialog-content>
   <mat-divider></mat-divider>
 
   <app-dialog-action-buttons