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/docs/chapter_greedy/index.md

@@ -0,0 +1,9 @@
+# 貪欲法
+
+![貪欲法](../assets/covers/chapter_greedy.jpg)
+
+!!! abstract
+
+    ひまわりは太陽の方を向き、常に自分にとって最大の成長を求めます。
+
+    貪欲な戦略は、一連の単純な選択を通じて、段階的に最良の答えへと導きます。