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/python/chapter_computational_complexity/iteration.py

@@ -0,0 +1,65 @@
+"""
+File: iteration.py
+Created Time: 2023-08-24
+Author: krahets (krahets@163.com)
+"""
+
+
+def for_loop(n: int) -> int:
+    """forループ"""
+    res = 0
+    # 1, 2, ..., n-1, n の合計をループ
+    for i in range(1, n + 1):
+        res += i
+    return res
+
+
+def while_loop(n: int) -> int:
+    """whileループ"""
+    res = 0
+    i = 1  # 条件変数を初期化
+    # 1, 2, ..., n-1, n の合計をループ
+    while i <= n:
+        res += i
+        i += 1  # 条件変数を更新
+    return res
+
+
+def while_loop_ii(n: int) -> int:
+    """whileループ（2つの更新）"""
+    res = 0
+    i = 1  # 条件変数を初期化
+    # 1, 4, 10, ... の合計をループ
+    while i <= n:
+        res += i
+        # 条件変数を更新
+        i += 1
+        i *= 2
+    return res
+
+
+def nested_for_loop(n: int) -> str:
+    """二重forループ"""
+    res = ""
+    # i = 1, 2, ..., n-1, n をループ
+    for i in range(1, n + 1):
+        # j = 1, 2, ..., n-1, n をループ
+        for j in range(1, n + 1):
+            res += f"({i}, {j}), "
+    return res
+
+
+"""Driver Code"""
+if __name__ == "__main__":
+    n = 5
+    res = for_loop(n)
+    print(f"\nforループの合計結果 res = {res}")
+
+    res = while_loop(n)
+    print(f"\nwhileループの合計結果 res = {res}")
+
+    res = while_loop_ii(n)
+    print(f"\nwhileループ（2つの更新）の合計結果 res = {res}")
+
+    res = nested_for_loop(n)
+    print(f"\n二重forループの走査結果 {res}")