New translations app-shelf.json (Japanese)

public/locales/ja/layout/app-shelf.json

@@ -0,0 +1,10 @@
+{
+  "accordions": {
+    "downloads": {
+      "text": "Your downloads"
+    },
+    "others": {
+      "text": "Others"
+    }
+  }
+}