Add monochrome icon.

[dav23r]

Suggesting to add monochrome layer to the app icon in order for it to be themable on modern Android versions.

For reference: https://developer.android.com/develop/ui/compose/system/icon_design_adaptive

[jambl3r]

is a simple black version sufficient?

[sds100]

this is easy for me to do with the foreground icon files i already have