Fix missing localization

Author: Gargron

lang/en.json

@@ -4,6 +4,7 @@
   "CJyF1e": "Continue to Mastodon",
   "EFcHaU": "HTML snippet",
   "HTxOva": "If your handle is <samp>@alice@mastodon.social</samp>, the domain is <samp>mastodon.social</samp>. You will be redirected to a page on your Mastodon server.",
+  "IX+poe": "does not seem to be a valid domain name.",
   "JBWS0c": "Link",
   "JJ5bOA": "Users can still customize the text before they post.",
   "K3r6DQ": "Delete",