Theme Engine: Notifications Background Transparency

[anthonycaccese]

Issue description

Hello team,

I think it would helpful to be able to remove or set different transparency for the notifications bubbles in the theme engine. It would enable themers to position theme elements without being concerned about the notification bubble being visually distracting when it displays.

This would be specifically helpful for small screen themes where layout options for theme elements can be a bit more limited.

As an example: here are screenshots from a small screen implementation (4" 1:1 screen) for Art Book Next where layout wise it made sense to display the battery/wifi indicators at the top right.

As you can see when notifications display the wifi/battery text shows through the bubble which can be a bit distracting.

I understand that there is a preference to keep notification UX consistently positioned (so that users can always rely on knowing where it will display) so was thinking maybe a compromise would be to allow themers to set its display transparency only - that could be the best of both worlds (consistent placement + remove the potential for visual distraction).

i've read through ThemeData.cpp to see but didn't see something that might be an option so thought it would be helpful to at least ask and see your thoughts. Please let me know what you think and I am glad to talk through use cases more.

Thank you for any feedback.