Add English translation for mute confirmation

src/i18n/en.json

@@ -938,6 +938,10 @@
     "message": "Message",
     "mute": "Mute",
     "muted": "Muted",
+    "mute_confirm_title": "Mute confirmation",
+    "mute_confirm": "Do you really want to mute {user}?",
+    "mute_confirm_accept_button": "Mute",
+    "mute_confirm_cancel_button": "Do not mute",
     "per_day": "per day",
     "remote_follow": "Remote follow",
     "remove_follower": "Remove follower",