Added icon

manifest.json

     "description": "Find mirrors for blocked websites",
     "version": "1.0",
 
+    "icons": {
+        "128": "icon-128.png"
+    },
+
     "browser_action": {
         "default_icon": "icon.png",
         "default_popup": "popup.html"
     },
+
     "permissions": [
         "storage",
         "tabs"