Add English translation for logout confirmation

src/i18n/en.json

@@ -137,6 +137,10 @@
     "login": "Log in",
     "description": "Log in with OAuth",
     "logout": "Log out",
+    "logout_confirm_title": "Logout confirmation",
+    "logout_confirm": "Do you really want to logout?",
+    "logout_confirm_accept_button": "Logout",
+    "logout_confirm_cancel_button": "Do not logout",
     "password": "Password",
     "placeholder": "e.g. lain",
     "register": "Register",