No desktop notifications if app is focused

### Description

When Element desktop app is focused, desktop notifications are disabled. If sound notifications are disabled (maybe due to #15023), you have almost zero feedback that somebody is speaking to you. If you've selected one community and the message comes from another (or no) community, the feedback is even less.

### Steps to reproduce

- Disable sound notifications
- Have room RA in community CA, and room RB in community CB
- Focus on CB
- Write on RB
- While you're writing, somebody writes in RA


As you can imagine, it's very easy to miss messages.

I think desktop notifications should still appear while you're using the app _and they come from a room that is not in focus_. Just like sound notifications.

Logs being sent: no

### Version information

- **Platform**: desktop
- **OS**: Fedora 33 silverblue
- **Version**: 1.7.16

Reproduce the desktop scenario with sound notifications disabled: focus on one community and send a message from a room in another community or outside one. Done means a desktop notification appears for an unfocused room while the app remains focused, without notifying for the room currently in focus.

Written by the indexing model from the issue text.