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.

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

ja/codes/python/modules/vertex.py

@@ -0,0 +1,20 @@
+# File: vertex.py
+# Created Time: 2023-02-23
+# Author: krahets (krahets@163.com)
+
+
+class Vertex:
+    """頂点クラス"""
+
+    def __init__(self, val: int):
+        self.val = val
+
+
+def vals_to_vets(vals: list[int]) -> list["Vertex"]:
+    """値のリストvalsを入力し、頂点のリストvetsを返す"""
+    return [Vertex(val) for val in vals]
+
+
+def vets_to_vals(vets: list["Vertex"]) -> list[int]:
+    """頂点のリストvetsを入力し、値のリストvalsを返す"""
+    return [vet.val for vet in vets]