Generalized image decoding and resizing logic

Summary:
public

Standardises the image decoding logic for all image sources, meaning we get the benefits of efficient downscaling of images from all sources, not just ALAssets.

Reviewed By: javache

Differential Revision: D2647083

fb-gh-sync-id: e41456f838e4c6ab709b1c1523f651a86ff6e623

Libraries/Image/RCTImageView.h

@@ -9,6 +9,7 @@
 
 #import <UIKit/UIKit.h>
 #import "RCTImageComponent.h"
+#import "RCTResizeMode.h"
 
 @class RCTBridge;
 @class RCTImageSource;