Once I've added my imported PNG icon files to the xcassets panel, is it OK to delete them from the project? After doing so, I notice that the images still appear in the assets panel, and I still get the right icon when I run the app. I also no longer get this errror:
resource fork, Finder information, or similar detritus not allowed
Command CodeSign failed with a nonzero exit code
This is a macOS app, if that makes any difference.