index.md: Use kramdown style for Announcements

index.md

@@ -14,9 +14,7 @@ description: >-
 
 {% if site.announcements %}
 {{ site.announcements.last }}
-<a href="{{ site.baseurl }}{% link announcements.md %}" class="btn btn-outline fs-3">
-  All Announcements
-</a>
+[Announcements]({{ site.baseurl }}{% link announcements.md %}){: .btn .btn-outline .fs-3 }
 {% endif %}
 
 ## Just the Class