Migrate to Zensical (#1869)

* Fix Russian Ruby code extraction.

* Add zensical configs.

overrides/partials/comments.html

@@ -0,0 +1,71 @@
+{% if page.meta.comments %}
+  {% if config.theme.language == 'zh' %}
+    {% set comm = "欢迎在评论区留下你的见解、问题或建议" %}
+    {% set lang = "zh-CN" %}
+  {% elif config.theme.language == 'zh-Hant' %}
+    {% set comm = "歡迎在評論區留下你的見解、問題或建議" %}
+    {% set lang = "zh-TW" %}
+  {% elif config.theme.language == 'en' %}
+    {% set comm = "Feel free to drop your insights, questions or suggestions" %}
+    {% set lang = "en" %}
+  {% elif config.theme.language == 'ja' %}
+    {% set comm = "ご意見、ご質問、ご提案があればぜひコメントしてください" %}
+    {% set lang = "ja" %}
+  {% elif config.theme.language == 'ru' %}
+    {% set comm = "Оставляйте свои идеи, вопросы и предложения в комментариях" %}
+    {% set lang = "ru" %}
+  {% endif %}
+
+  <!-- Check-in button above comments -->
+  {% include "partials/checkin.html" ignore missing %}
+
+  <h5 align="center" id="__comments">{{ comm }}</h5>
+
+  <!-- Insert generated snippet here -->
+  <script
+    src="https://giscus.app/client.js"
+    data-repo="krahets/hello-algo"
+    data-repo-id="R_kgDOIXtSqw"
+    data-category="Announcements"
+    data-category-id="DIC_kwDOIXtSq84CSZk_"
+    data-mapping="pathname"
+    data-strict="1"
+    data-reactions-enabled="1"
+    data-emit-metadata="1"
+    data-input-position="top"
+    data-theme="light"
+    data-lang="{{ lang }}"
+    crossorigin="anonymous"
+    async
+  >
+  </script>
+  <!-- Synchronize Giscus theme with palette -->
+  <script>
+    var giscus = document.querySelector("script[src*=giscus]")
+
+    /* Set palette on initial load */
+    var palette = __md_get("__palette")
+    if (palette && typeof palette.color === "object") {
+      var theme = palette.color.scheme === "slate" ? "dark_dimmed" : "light"
+      giscus.setAttribute("data-theme", theme) 
+    }
+
+    /* Register event handlers after documented loaded */
+    document.addEventListener("DOMContentLoaded", function() {
+      var ref = document.querySelector("[data-md-component=palette]")
+      ref.addEventListener("change", function() {
+        var palette = __md_get("__palette")
+        if (palette && typeof palette.color === "object") {
+          var theme = palette.color.scheme === "slate" ? "dark_dimmed" : "light"
+
+          /* Instruct Giscus to change theme */
+          var frame = document.querySelector(".giscus-frame")
+          frame.contentWindow.postMessage(
+            { giscus: { setConfig: { theme } } },
+            "https://giscus.app"
+          )
+        }
+      })
+    })
+  </script>
+{% endif %}