adds link to design codes prototype

index.html

@@ -75,6 +75,12 @@ <h2 class="govuk-heading-m">Services and tools</h2>
         </p>
         <p class="govuk-body govuk-!-font-size-16">Prototype tool for creating data that meets the development plan data standard.</p>
       </li>
+      <li class="govuk-list__item govuk-!-margin-bottom-12">
+        <p class="govuk-body govuk-!-margin-bottom-1">
+          <a href="https://design-code-prototype.planning-data.dev/" class="govuk-link govuk-!-font-weight-bold">Design codes prototype</a>
+        </p>
+        <p class="govuk-body govuk-!-font-size-16">to show how data found on the Planning Data Platform can be easily presented in different ways on other websites.</p>
+      </li>
     </ul>
   </div>
-</div>
+</div>