unsent messages get missed if you don't look at the room

[uhoreg]

If a message fails to send, it's easy the alert doesn't show up anywhere until you go back to the room that you tried to send it from. It would probably be nice to show a badge in the room list.

[turt2live]

Duplicate of #1351

Related:

• when returning back online, prompt user with dialog if they want to resend all sent messages #4824
• Unsent messages in a room should still cause it to rise in the RoomList #1898