Add extension icon set and manifest icon configuration

manifest.json

@@ -42,10 +42,16 @@
     "src/background.js"
   ]
 },
-
   "action": {
     "default_title": "VendorGet-IV",
-    "default_popup": "src/popup/popup.html"
+    "default_popup": "src/popup/popup.html",
+    "default_icon": {
+      "16": "icons/vg-16.png",
+      "32": "icons/vg-32.png",
+      "48": "icons/vg-48.png",
+      "96": "icons/vg-96.png",
+      "128": "icons/vg-128.png"
+    }
   },
 
   "content_scripts": [
@@ -66,7 +72,6 @@
       "matches": ["<all_urls>"]
     }
   ],
-
   "browser_specific_settings": {
     "gecko": {
       "id": "vendorget@local"