Skia rgb32 not working

[djowel]

Related to 5ed6085

Pinging bnert

I'm getting weird results when the pixel format is rgb32:

artist/lib/include/artist/image.hpp

Line 34 in 5ae0469

rgb32, // First byte is Alpha of 1, or ignored

I'll remove rgb32 for now. rgba32 is most important and it's working just fine. I'd appreciate it if you can take a look.

I haven't tested the other options gray8 and rgb16. It's a good idea to have these tested as well.