docs: add Japanese translate documents (#1812)

* docs: add Japanese documents (`ja/docs`)

* docs: add Japanese documents (`ja/codes`)

* docs: add Japanese documents

* Remove pythontutor blocks in ja/

* Add an empty at the end of each markdown file.

* Add the missing figures (use the English version temporarily).

* Add index.md for Japanese version.

* Add index.html for Japanese version.

* Add missing index.assets

* Fix backtracking_algorithm.md for Japanese version.

* Add avatar_eltociear.jpg. Fix image links on the Japanese landing page.

* Add the Japanese banner.

---------

Co-authored-by: krahets <krahets@163.com>

ja/codes/cpp/chapter_greedy/max_capacity.cpp

@@ -0,0 +1,39 @@
+/**
+ * File: max_capacity.cpp
+ * Created Time: 2023-07-21
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* 最大容量：貪欲法 */
+int maxCapacity(vector<int> &ht) {
+    // i、j を初期化し、配列の両端で分割させる
+    int i = 0, j = ht.size() - 1;
+    // 初期最大容量は 0
+    int res = 0;
+    // 2つの板が出会うまで貪欲選択をループ
+    while (i < j) {
+        // 最大容量を更新
+        int cap = min(ht[i], ht[j]) * (j - i);
+        res = max(res, cap);
+        // より短い板を内側に移動
+        if (ht[i] < ht[j]) {
+            i++;
+        } else {
+            j--;
+        }
+    }
+    return res;
+}
+
+/* ドライバーコード */
+int main() {
+    vector<int> ht = {3, 8, 5, 2, 7, 7, 3, 4};
+
+    // 貪欲アルゴリズム
+    int res = maxCapacity(ht);
+    cout << "最大容量は " << res << " です" << endl;
+
+    return 0;
+}