Add loading spinner to comment-list

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

 <div fxLayout="row" fxLayoutAlign="center">
   <div fxLayout="column" fxLayoutGap="20px">
+    <mat-progress-spinner *ngIf="isLoading" mode="indeterminate"></mat-progress-spinner>
       <div *ngFor="let comment of comments">
         <mat-card>
           <mat-card-content>

src/app/comment-list/comment-list.component.ts

@@ -19,6 +19,7 @@ export class CommentListComponent implements OnInit {
   userRole: UserRole;
   user: User;
   comments: Comment[];
+  isLoading = true;
 
   constructor(
     protected authenticationService: AuthenticationService,
@@ -51,6 +52,7 @@ export class CommentListComponent implements OnInit {
       this.commentService.searchComments(roomId, this.user.id)
         .subscribe(comments => this.comments = comments);
     }
+    this.isLoading = false;
   }
 
   setRead(comment: Comment): void {