Add langswitcher plugin v3.3.0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plugins/langswitcher/templates/partials/langswitcher.html.twig

@@ -0,0 +1,15 @@
+{% extends 'partials/langswitcher-logic.html.twig' %}
+
+{% block language_block_start %}
+<ul class="langswitcher">
+{% endblock %}
+
+{% block language_block_end %}
+</ul>
+{% endblock %}
+
+{% block language_item %}
+    {% if show_language %}
+    <li><a href="{{ lang_url ~ uri.params ~ (uri.query|length > 1 ? '?' ~ uri.query) }}" class="external {{ active_class }}">{% include 'partials/langswitcher-' ~ display_format ~ '.html.twig' %}</a></li>
+    {% endif %}
+{% endblock %}