add data-test-class to download button

alfa-client/libs/binary-file/src/lib/binary-file2-container/binary-file2/binary-file2.component.html

@@ -5,6 +5,7 @@
   (click)="downloadFile()"
   [attr.aria-label]="'Anhang: Dateiname: ' + file.name"
   [isLoading]="isLoading"
+  data-test-class="download-file-button"
 >
   <div close class="flex-shrink self-center">
     <button