Add option for Dank Bar Notification Widget to be invisble/zero width when empty

### Feature Description

I'd like an option for the notification bell on the Dank Bar to be not present when there are no notifications and to appear when there are notifications.

### Use Case

I find the presence of the bell to indicate to me there are notifications to view and the small dot to indicate notifications to be a little too hard to notice. Present/invisible would solve both of these issues for me.

### Compositor(s)

All compositors

### If Other, please specify

_No response_

### Proposed Solution

A toggle for visibility being located in a three-dot menu within Settings > Widgets rather than the gear from the widget itself, since if the option were located in the gear menu from the widget itself you wouldn't be able to access it unless a notification were present. I would imagine it could be simple toggle to only show the widget when notifications were present and when not would make the widget zero width so that it doesn't take up space on the bar.

### Alternatives/Existing Solutions

None that I'm aware of as a drop in solution.

No files, tests, or entry points are named. Start by locating the Dank Bar Notification Widget and the Settings > Widgets menu, then trace how notification presence affects the widget. Done means the option is configurable there and the widget becomes invisible and zero width without notifications, while appearing when notifications exist.

Written by the indexing model from the issue text.