Notifications should have another level that rings once when there's a new message, until room is visited

**Is your suggestion related to a problem? Please describe.**
There is a big jump between notification levels:
- All messages: Every 🔔 single 🔔 message 🔔 makes 🔔 all 🔔 my 🔔 devices 🔔 beep! 🔔
- Mentions only: Every mention 🔔 is notified, but only mentions. 🔔
- Mute. 😐

So sometimes people are having a friendly chat in one of my all-messages room, and it's very noisy even when I'm not interested in that conversation, or I can't go there yet.

**Describe the solution you'd like**
I think there should be another level that notifies me *once* per room, until I visit that room.
This way, long conversations will only trigger one notification, but if I can't read it right now, at least my devices won't keep notifying me.

Bonus: This could reset every few hours / day, so I'd get another notification as a reminder.

**Describe alternatives you've considered**
When things get too noisy, I have to either lower the notification level for that room (at the risk of forgetting about it, and then missing new messages later on).
Or I have to turn my phone to "quiet" mode, but once again I could miss other notifications (from Riot or other apps).

**Additional context**
N/A