Add buttons that require extra spacing

These get added using the macro as usual, but with the special spacing
classes added to ensure there's no change to their appearance.

app/templates/views/service-settings/preview-letter-branding.html

@@ -1,5 +1,7 @@
 {% extends "views/platform-admin/_base_template.html" %}
 {% from "components/form.html" import form_wrapper %}
+{% from "components/button/macro.njk" import govukButton %}
+
 {% block per_page_title %}
   Preview letter branding
 {% endblock %}
@@ -14,7 +16,7 @@
         <div class="form-group">
           {{ form.hidden_tag() }}
           <div class="page-footer">
-            <button type="submit" class="button">Save</button>
+            {{ govukButton({ "text": "Save", "classes": "govuk-!-margin-right-2" }) }}
             <a class="page-footer-back-link" href="{{ url_for('main.service_settings', service_id=service_id) }}">Back to service settings</a>
           </div>
         </div>

app/templates/views/templates/template.html

@@ -4,6 +4,7 @@
 {% from "components/page-footer.html" import page_footer %}
 {% from "components/textbox.html" import textbox %}
 {% from "components/api-key.html" import api_key %}
+{% from "components/button/macro.njk" import govukButton %}
 
 {% block service_page_title %}
   {{ page_title_folder_path(current_service.get_template_path(template._template)) }}
@@ -24,7 +25,7 @@
         </ul>
         <form method='post'>
           <input type="hidden" name="csrf_token" value="{{ csrf_token() }}" />
-          <button type="submit" class="button" name="delete">Confirm</button>
+          {{ govukButton({ "text": "Confirm", "classes": "govuk-button--warning govuk-!-margin-top-2" }) }}
         </form>
       {% endcall %}
     </div>