add a preserveImages prop that allows the (iOS) impl to keep images

ios/GLCanvas.h

@@ -9,6 +9,7 @@
 @property (nonatomic) BOOL autoRedraw;
 @property (nonatomic) BOOL eventsThrough;
 @property (nonatomic) BOOL visibleContent;
+@property (nonatomic) BOOL preserveImages;
 @property (nonatomic) NSNumber *nbContentTextures;
 @property (nonatomic) NSNumber *renderId;
 @property (nonatomic) NSNumber *pixelRatio;

ios/GLCanvas.m

@@ -183,7 +183,10 @@ RCT_NOT_IMPLEMENTED(-init)
   @autoreleasepool {
 
     NSDictionary *prevImages = _images;
-    NSMutableDictionary *images = [[NSMutableDictionary alloc] init];
+    NSMutableDictionary *images =
+      self.preserveImages
+      ? _images.mutableCopy
+      : [[NSMutableDictionary alloc] init];
 
     GLRenderData * (^traverseTree) (GLData *data);
     __block __weak GLRenderData * (^weak_traverseTree)(GLData *data);

ios/GLCanvasManager.m

@@ -25,6 +25,7 @@ RCT_EXPORT_MODULE();
 
 RCT_EXPORT_VIEW_PROPERTY(nbContentTextures, NSNumber);
 RCT_EXPORT_VIEW_PROPERTY(autoRedraw, BOOL);
+RCT_EXPORT_VIEW_PROPERTY(preserveImages, BOOL);
 RCT_EXPORT_VIEW_PROPERTY(data, GLData);
 RCT_EXPORT_VIEW_PROPERTY(renderId, NSNumber);
 RCT_EXPORT_VIEW_PROPERTY(pixelRatio, NSNumber);