Underlign selected category

src/app/store/store.component.html

@@ -10,7 +10,7 @@
                 <button class="btn btn-block btn-outline-primary" (click)="changeCategory()">
                     Home
                 </button>
-                <button *ngFor="let category of categories" class="btn btn-outline-primary btn-block" (click)="changeCategory(category)">
+                <button *ngFor="let category of categories" [class.active]="category == selectedCategory" class="btn btn-outline-primary btn-block" (click)="changeCategory(category)">
                     {{category}}
                 </button>
             </div>