Notifications should be expanded on hover

[naipotato]

Recently #63 has been merged, but this PR implies that all notifications will have 2 lines as maximum, which I think is not always the expected behaviour. For example, sometimes, you want to read the whole msg directly from the notification, without the need of opening the app. So I think it would be cool to add a behaviour which allows to the user to expand notifications when hovering with the cursor