Add icons variants for required resolutions (#1017)

* Add icons variants for required resolutions

* Optimize PNG's size

Even without centralizing the resources, we can already save a few bytes.
The total size was reduced by 75%.

* Replace iTunes variants by a very compact transparent image

This will never hit the AppStore anyway.

* Replace images by lossless optimized variants

The previous optimization pass was lossy. This PR replace images with an optimized lossless variant of the original.

* Restore original iPhone icons

I don't know why images that were supposedly losslessly optimized by ImageOptim were less vibrant than the original.
I restored them by their original variants. Upscaled variants are less vibrant though, but I guess it's acceptable without access to the original vector source.

* Fix color space

ImageOptim seems to change the color space when it optimizes files losslessly.
I've created new variants with Pixelmator Pro and exported as web-compressed from there instead.

Author: tgrapperon

Examples/CaseStudies/SwiftUICaseStudies/Assets.xcassets/AppIcon.appiconset/[email protected]

@@ -31,6 +31,7 @@
       "size" : "40x40"
     },
     {
+      "filename" : "[email protected]",
       "idiom" : "iphone",
       "scale" : "2x",
       "size" : "60x60"
@@ -77,16 +78,19 @@
       "size" : "76x76"
     },
     {
+      "filename" : "[email protected]",
       "idiom" : "ipad",
       "scale" : "2x",
       "size" : "76x76"
     },
     {
+      "filename" : "[email protected]",
       "idiom" : "ipad",
       "scale" : "2x",
       "size" : "83.5x83.5"
     },
     {
+      "filename" : "transparent.png",
       "idiom" : "ios-marketing",
       "scale" : "1x",
       "size" : "1024x1024"