[Keyboard] add macro pad "Shiro" (#6338)

* add keyboard new macro pad "Kuro"

* change main readme.md

* remove not used code from default/keymap.c

* Remove unnecessary code

* Supports info.json

* removed back slash and not used functions.

* update at product link. add japanese messages.

keyboards/shiro/keymaps/check/readme.md

@@ -0,0 +1 @@
+# The default keymap for Shiro