Include the Shim links with button role script from the frontend toolkit

Links styled to look like buttons lack button behaviour. This script will allow them to be triggered with a space key after they’ve been focused, to match standard buttons.

By default, this behaviour will only be applied to links with a role of button.

app/views/includes/scripts.html

@@ -3,6 +3,7 @@
 <!-- govuk_frontend_toolkit js -->
 <script src="/public/javascripts/vendor/polyfills/bind.js"></script>
 <script src="/public/javascripts/govuk/selection-buttons.js"></script>
+<script src="/public/javascripts/govuk/shim-links-with-button-role.js"></script>
 
 <!-- govuk_elements js -->
 <script src="/public/javascripts/vendor/details.polyfill.js"></script>