treewide: enable Italian language

_config.yml

@@ -197,7 +197,7 @@ exclude: [
   _pages/fr_FR,
   _pages/he_IL,
   _pages/hu_HU,
-  _pages/it_IT,
+  # _pages/it_IT,
   _pages/ja_JP,
   _pages/ko_KR,
   _pages/nl_NL,
@@ -331,3 +331,9 @@ defaults:
       type: pages
     values:
       permalink: /index:output_ext
+  - scope:
+      path: "_pages/it_IT"
+      type: pages
+    values:
+      permalink: /it_IT/:basename:output_ext
+      lang: it

_includes/masthead.html

@@ -54,6 +54,7 @@
             {% assign langless_url = "" %}
           {% endif %}
           <li class="masthead__menu-item"><a href="{{ site.url }}/{{ langless_url }}">English</a></li>
+          <li class="masthead__menu-item"><a href="{{ site.url }}/it_IT/{{ langless_url }}">Italiano</a></li>
         </ul>
         <button class="greedy-nav__toggle hidden" type="button">
           <span class="visually-hidden">{{ site.data.ui-text[site.locale].menu_label | default: "Toggle menu" }}</span>