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/java/chapter_stack_and_queue/stack.java

@@ -0,0 +1,40 @@
+/**
+ * File: stack.java
+ * Created Time: 2022-11-25
+ * Author: krahets (krahets@163.com)
+ */
+
+package chapter_stack_and_queue;
+
+import java.util.*;
+
+public class stack {
+    public static void main(String[] args) {
+        /* スタックを初期化 */
+        Stack<Integer> stack = new Stack<>();
+
+        /* 要素をプッシュ */
+        stack.push(1);
+        stack.push(3);
+        stack.push(2);
+        stack.push(5);
+        stack.push(4);
+        System.out.println("スタック stack = " + stack);
+
+        /* スタックトップ要素にアクセス */
+        int peek = stack.peek();
+        System.out.println("スタックトップ要素 peek = " + peek);
+
+        /* 要素をポップ */
+        int pop = stack.pop();
+        System.out.println("ポップした要素 = " + pop + "、ポップ後 " + stack);
+
+        /* スタックの長さを取得 */
+        int size = stack.size();
+        System.out.println("スタックの長さ size = " + size);
+
+        /* 空かどうかを判定 */
+        boolean isEmpty = stack.isEmpty();
+        System.out.println("スタックが空か = " + isEmpty);
+    }
+}