feat(templates/header.html): add language switchen in header

kursy/templates/header.html

@@ -9,6 +9,18 @@
         <a href="{% url 'account_login' %}" class="hover:underline">{% trans "Login" %}</a>
         <a href="{% url 'account_signup' %}" class="hover:underline">{% trans "Sign Up" %}</a>
       {% endif %}
+      <div class="inline-block relative group">
+        <form action="{% url 'set_language' %}" method="post">
+          {% csrf_token %}
+          <button type="button" class="hover:underline focus:outline-none">{% get_current_language as LANGUAGE_CODE %}{{ LANGUAGE_CODE|upper }}</button>
+          <div class="absolute right-0 w-32 bg-white text-black rounded-md shadow-lg hidden group-hover:block">
+            {% get_available_languages as LANGUAGES %}
+            {% for lang_code, lang_name in LANGUAGES %}
+              <button name="language" value="{{ lang_code }}" class="block w-full text-left rounded-md px-4 py-2 hover:bg-gray-200">{{ lang_name }}</button>
+            {% endfor %}
+          </div>
+        </form>
+      </div>
     </nav>
   </div>
 </header>