Enhancement for arrows on image carousel

[madsrh]

The difference between the active and deactivated arrows in the image carousel are too subtle IMHO. I think a better solution would be if the images could just loop ♾️ or alternatively, to hide the left arrow on the first image (and right arrow for the last ofc).

For accessibility the keyboard left/right arrows should work when I click the arrows, the dots and when the image is enlarged.

[Feichtmeier]

Could you move this issue to yaru_widgets?
It is a component from there (thanks to paul!) :)

[madsrh]

Moved to ubuntu/yaru.dart#208