Theme-aware splash screen logos

[DierkDroth]

It would be great to have theme-aware logos for the splash screen:

• one logo for LIGHT theme
• a different one (well, most likely the logo above, just with 'revereted' colors) for DARK theme

I'm aware that I could custom code that logic in index.html. However, AFAIK this is not possible with AppManifest.js (where also is a splash instance defined)