revert: accidental removal of some needed translation source strings

public/language/en-GB/email.json

@@ -37,6 +37,10 @@
 	"digest.subject": "Digest for %1",
 	"digest.title": "Your Daily Digest",
 
+	"notif.chat.subject": "New chat message received from %1",
+	"notif.chat.cta": "Click here to continue the conversation",
+	"notif.chat.unsub.info": "This chat notification was sent to you due to your subscription settings.",
+
 	"notif.post.unsub.info": "This post notification was sent to you due to your subscription settings.",
 
 	"notif.cta": "To the forum",