Updated OSCAR.icns for macOS.

Added 2 missing icons.
Added hi-res Retina icons.
Updated README for icons with more Mac details.

Building/Icons/README

@@ -5,17 +5,44 @@ is in Photshop Notes.xlsm, an Excel worksheet.
 
 Smaller icons require manual editing for best appearance.
 
+For Windows-----------
+
 Windows .ico file should contain 16x16, 32x32, 48x48, and 256x256 images.  We
 also include 24x24 for Windows XP compatibility.
 A .ico file can be built at the website icoconvert.com.
 
-MacOS .icns file should contain:
+For macOS -----------	
 
-    Icon size (@1x) 	                Icon size (@2x)
-    512px × 512px (512pt × 512pt @1x) 	1024px × 1024px (512pt × 512pt @2x)
-    256px × 256px (256pt × 256pt @1x) 	512px × 512px (256pt × 256pt @2x)
-    128px × 128px (128pt × 128pt @1x) 	256px × 256px (128pt × 128pt @2x)
-    32px × 32px (32pt × 32pt @1x) 	    64px × 64px (32pt × 32pt @2x)
-    16px × 16px (16pt × 16pt @1x) 	    32px × 32px (16pt × 16pt @2x)
+macOS naming conventions for icons:
+icon_64x64.png 		(for standard resolution)
+icon_64x64@2x.png 	(for hi-res Retina icons)
 				
-The .icns file can be edited on Windows using the Greenfish Icon Editor.
+The macOS hi-res icons are double the size of the standard icons.
+ex. the icon_128x128@2x is actually a 256x256 image.  Mac automatically 
+selects the correct one based on the type of display.
+					
+macOS defaults to using pt (point) instead of px (pixel) for image size. Set the image DPI to 72 px for the 
+original image and it should not cause any sizing issues if using px. 
+
+Mac has a native command line tool, "iconutil", for creating *.icns file.
+Create the images, listed below, in a folder named oscar-icons.iconset (note the extension on a folder)
+For more information check "man iconutil" or the Mac Developer documentation at:
+https://developer.apple.com/library/archive/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/Optimizing/Optimizing.html
+
+macOS .icns file should contain:
+
+    (Icon size in px)
+    
+    icon_16x16.png
+    icon_16x16@2x.png	(32x32 image)
+    icon_32x32.png
+    icon_32x32@2x.png	(64x64 image)
+    icon_128x128.png
+    icon_128x128@2x.png	(256x256 image)
+    icon_256x256.png
+    icon_256x256@2x.png	(512x512 image)
+    icon_512x512.png
+    icon_512x512@2x.png	(1024x1024 image)
+	
+
+The macOS *.icns file can also be edited on Windows using the Greenfish Icon Editor.