initWithSVGData

Adds convenience initialisers to platform images;

UIImage(svgData: Data)
UIImage(contentsOfSVGFile path: String)

NSImage(svgData: Data)
NSImage(contentsOfSVGFile path: String)

And exports to Objective-C

- (instancetype) initWithSVGData: (NSData *)
- (instancetype) initWithContentsOfSVGFile: (NSString *)