Migrate to Zensical (#1869)

* Fix Russian Ruby code extraction.

* Add zensical configs.

overrides/main.html

@@ -9,6 +9,8 @@
     {% set announcements = 'Welcome to contribute to Chinese-to-English translation! For more details, please refer to <a href="https://github.com/krahets/hello-algo/blob/main/en/CONTRIBUTING.md">CONTRIBUTING.md</a>.' %}
 {% elif config.theme.language == 'ja' %}
     {% set announcements = '日本語版審閱者を募集しています！詳細は <a href="https://github.com/krahets/hello-algo/blob/main/ja/CONTRIBUTING.md">CONTRIBUTING.md</a> を参照してください。' %}
+{% elif config.theme.language == 'ru' %}
+    {% set announcements = 'Приглашаем вас участвовать в развитии русской версии! Подробнее <a href="/ru/chapter_appendix/contribution/">здесь</a>.' %}
 {% endif %}
 <div class="banner-svg">
     <svg xmlns="http://www.w3.org/2000/svg"
@@ -18,4 +20,4 @@
     </svg>
     <span>{{ announcements }}</span>
 </div>
-{% endblock %}
+{% endblock %}