add basic language switcher

_includes/footer.njk

@@ -1,6 +1,13 @@
 <footer>
   <div>
-    <div>[language switcher]</div>
+    {% set otherLang = page.url | locale_links | first %}
+    <a href="{{otherLang.url}}" lang="{{otherLang.lang}}" hreflang="{{otherLang.lang}}">
+      {% if otherLang.lang == "de" %}
+        Deutsche Version 🇩🇪
+      {% else %}
+        English Version 🇬🇧/🇺🇸
+      {% endif %}
+    </a>
     <nav>
       {{ collections.footerNav | pageLang | eleventyNavigation | eleventyNavigationToHtml | safe }}
     </nav>