Log warnings in ImageAsset.image and SystemImage.image when loadImage() fails

[mpospese]

Let's log to console from var image: UIImage when loadImage() returns nil and we resort to the fallback image.
(This is preferable to logging from loadImage() which can be expected to return nil under certain unit tests.)

See how YMatterType logs when fonts don't load and let's adopt a similar pattern for declaring the Logger to use.
This will be iOS 14+.

[WestonHanners]

Can you cite an example of the YMatterType logging you speak of?

[mpospese]

import os

extension Typography {
    fileprivate static let logger = Logger(subsystem: "YMatterType", category: "fonts")
}

and then

        guard let font = UIFont(name: name, size: pointSize) else {
            // Fallback to system font and log a message.
            Typography.logger.warning("Custom font \(name) not properly installed.")