Feature request: Show a notification counter in multi-column mode

**Is your feature request related to a problem? Please describe.**
I love the multi-column mode in Phanpy, so, thank you for building that. But, there no indication if I've got new notifications on the main view. I have to click the menu button and go to the notifications page to see them.

**Describe the solution you'd like**
If possible, please include a notifications button in the multi-column view that indicates if I have unseen notifications either via a red dot or a number. A bonus feature could be than on clicking the button the notifications list opens in a side-drawer like panel.

**Describe alternatives you've considered**
I can obviously add a column for notifications but a button based temporary panel view is more suited for notifications in case of low volume users like myself.

Thanks again for making Phanpy. Its a really wonderful experience to use it.