Add Japanese localization (#631)

* Update en.ts: add the copyright header

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Copy en.ts to ja.ts for tracking

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Add ja to App.tsx

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Update ja.ts

Reuse 752dc7a4cf/src/i18n/en.ts

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Add and enable ra-language-japanese

Available at https://github.com/bicstone/ra-language-japanese

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

---------

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>
Co-authored-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

package.json

@@ -62,6 +62,7 @@
     "vite-plugin-version-mark": "^0.1.4"
   },
   "dependencies": {
+    "@bicstone/ra-language-japanese": "^5.6.3",
     "@emotion/react": "^11.14.0",
     "@emotion/styled": "^11.14.0",
     "@haleos/ra-language-german": "^1.0.0",