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/cpp/utils/common.hpp

@@ -0,0 +1,28 @@
+/**
+ * File: common.hpp
+ * Created Time: 2021-12-19
+ * Author: krahets (krahets@163.com)
+ */
+
+#pragma once
+
+#include <algorithm>
+#include <chrono>
+#include <deque>
+#include <iostream>
+#include <list>
+#include <queue>
+#include <random>
+#include <set>
+#include <stack>
+#include <string>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+#include "list_node.hpp"
+#include "print_utils.hpp"
+#include "tree_node.hpp"
+#include "vertex.hpp"
+
+using namespace std;