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_searching/two_sum.py

@@ -0,0 +1,42 @@
+"""
+File: two_sum.py
+Created Time: 2022-11-25
+Author: krahets (krahets@163.com)
+"""
+
+
+def two_sum_brute_force(nums: list[int], target: int) -> list[int]:
+    """方法一：ブルートフォース列挙"""
+    # 二重ループ、時間計算量は O(n^2)
+    for i in range(len(nums) - 1):
+        for j in range(i + 1, len(nums)):
+            if nums[i] + nums[j] == target:
+                return [i, j]
+    return []
+
+
+def two_sum_hash_table(nums: list[int], target: int) -> list[int]:
+    """方法二：補助ハッシュテーブル"""
+    # 補助ハッシュテーブル、空間計算量は O(n)
+    dic = {}
+    # 単一ループ、時間計算量は O(n)
+    for i in range(len(nums)):
+        if target - nums[i] in dic:
+            return [dic[target - nums[i]], i]
+        dic[nums[i]] = i
+    return []
+
+
+"""ドライバーコード"""
+if __name__ == "__main__":
+    # ======= テストケース =======
+    nums = [2, 7, 11, 15]
+    target = 13
+
+    # ====== ドライバーコード ======
+    # 方法一
+    res: list[int] = two_sum_brute_force(nums, target)
+    print("方法一の結果 =", res)
+    # 方法二
+    res: list[int] = two_sum_hash_table(nums, target)
+    print("方法二の結果 =", res)