Use app icon in Safari extension preferences list

Safari's extension preferences displayed the toolbar icon (gray cloud
outline) instead of the colorful app icon. The manifest.json "icons"
field is used for the extension list, while "action.default_icon" is
used for the toolbar.

Added separate app icon PNGs (copied from AppIcon.appiconset) and
updated manifest.json to use them for the top-level icons field.
The toolbar continues to use the simple gray icons.

Author: bartTC

CF Cache Status/CF Cache Status Extension/Resources/images/app-icon-128.png

@@ -4,10 +4,10 @@
   "version": "1.0",
   "description": "Shows CDN cache status (HIT/MISS) for the current page. Supports Cloudflare, CloudFront, Fastly, Akamai, and more.",
   "icons": {
-    "16": "images/icon-16.png",
-    "32": "images/icon-32.png",
-    "48": "images/icon-48.png",
-    "128": "images/icon-128.png"
+    "16": "images/app-icon-16.png",
+    "32": "images/app-icon-32.png",
+    "48": "images/app-icon-48.png",
+    "128": "images/app-icon-128.png"
   },
   "action": {
     "default_popup": "popup.html",