Top level offline banner when no WiFi or cellular network can be reached

[ShirleyNekoDev]

Description

When you have no WiFi or cellular network, it is futile to load each data source. Instead, they can be directly loaded from cache and wait for internet to become available again without showing a reload option. The missing internet option can be shown as a global banner at the top of the screen.

This of course differs from the connection error handling of each widget. These will load from their specific source and show an error and refresh option after timeouts or the like.