Adds hands-on learning for Search link to the landing page (elastic#1…

…16007)

Co-authored-by: Liam Thompson <32779855+leemthompo@users.noreply.github.com>

docs/reference/landing-page.asciidoc

@@ -79,6 +79,11 @@
 
 <h3 class="gtk">Get to know Elasticsearch</h3>
 
+<p>
+<em>Demos:</em>
+  <a href="https://www.elastic.co/demo-gallery?solutions=search&features=null&type=hands-on-learning">Hands-on learning for Search</a>
+</p>
+
 <p>
   <em>New webinar:</em>
   <a href="https://www.elastic.co/virtual-events/architecting-search-apps-on-google-cloud">Architect search apps with Google Cloud</a>