Add V3 info on landing page

Signed-off-by: Tushar Goel <tushar.goel.dav@gmail.com>

Author: TG1999

vulnerabilities/templates/index.html

@@ -33,6 +33,9 @@
                 </a>
             </p>
         </div>
+        <div class="notification is-info is-light has-text-centered">
+            ATTENTION: We will be deprecating V1 and V2 API by 30th June 2026. V3 endpoint is live now. Please migrate to V3 API before the deprecation date. For more details, please refer to this <a href="https://aboutcode-org.github.io/www.aboutcode.org/blog/vcio-migration-announcement-aboutcode" target="_blank" class="has-text-link is-underlined">blog</a>.
+        </div>
     </div>
 </section>
 {% endblock %}