Lots of fixes to "media threads"

src/assets/translations/en.json

@@ -62,7 +62,9 @@
     "user_was_banned_you": "You were kicked and banned from the chat.",
     "user_joined": "{user} joined the chat",
     "user_left": "{user} left the chat",
+    "someone": "Someone",
     "user_said": "{user} said:",
+    "sent_media": "Sent {count} media items.",
     "file_prefix": "File: ",
     "edited": "(edited)",
     "download_progress": "{percentage}% downloaded",