Showing read receipts in the room list

Would be cool if the room list could indicate if the last message was read.

* Indication either by the other person’s avatar or by a checkbox, or other markup (like background color), or by showing unread messages greyed out.
- Indication of transmission errors would also fit into this, so guess icons would be best.
* For DM rooms: Distinction between “not yet read” and “the last message was sent from the other person” is necessary.
* For bigger rooms: Maybe indicating “partly read” and “read by all” (except bots etc.) would be helpful in some cases, as then people would be able to know that at least one person read the message (what sometimes is enough).