feat: Add app icon in the console

[feinstein]

I would like to add app icons in my "Shorebird Apps" list.

I manage a bunch of apps in an agency and it makes it easier to visually find the app I want if I can add app icons to the "Shorebird Apps" list. Codemagic has a similar feature.

[eseidel]

Makes sense. We do seem to have a lot of "white label app" customers with lots of apps.