Support for UnifiedPush on Linux

### Your use case

#### What would you like to do?
Add support for push notifications on desktop Linux via UnifiedPush
#### Why would you like to do it?
UnifiedPush has a criminally low adoption rate on Android, let alone on Linux where, to my knowledge, only NeoChat makes use of it. It'd be nice for the reference Matrix client to be on the cutting edge of features and adopt push notifications (even if just as a toggle) so as to not have it running in the background to receive notifications.
#### How would you like to achieve it?
For now, KDE's KUnifiedPush is the only implementation of it, so targetting it would probably be the most practical move.

### Have you considered any alternatives?

_No response_

### Additional context

_No response_