[Docs] Japanese translation of docs/keycodes.md (qmk#10192)

* copy 'keycodes.md'.

* Translated 'keycodes.md'.

* Fixed typo.

* Fixed typo.

* Apply suggestions from code review

Co-authored-by: shela <[email protected]>
Co-authored-by: Takeshi ISHII <[email protected]>

* update based on comment.

* update based on comment.

* Update docs/ja/keycodes.md

* update based on comment.

Co-authored-by: Takeshi ISHII <[email protected]>

* update based on comment.

Co-authored-by: Takeshi ISHII <[email protected]>

* update based on comment.

Co-authored-by: Takeshi ISHII <[email protected]>

* Update docs/ja/keycodes.md

Co-authored-by: Takeshi ISHII <[email protected]>

* update based on comment.

Co-authored-by: Takeshi ISHII <[email protected]>

Co-authored-by: shela <[email protected]>
Co-authored-by: Takeshi ISHII <[email protected]>