Link to the demonstration service from the docs front page.

Author: simonwo

lib/importer/assets/docs/index.html

@@ -70,6 +70,9 @@ <h1 class="x-govuk-masthead__title">
                             <path fill="currentColor" d="M0 0h13l20 20-20 20H0l20-20z" />
                         </svg>
                     </a>
+                    <p class="x-govuk-masthead__description" style="font-size: 100%">
+                        You can also <a href="https://data-importer.register-dynamics.co.uk" target="_blank">try a demo service</a> built with this Kit.
+                    </p>
                 </div>
                 <div class="govuk-grid-column-one-half-from-desktop">
                     <div class="x-govuk-masthead__image">