added firefox app id key

manifest.json

@@ -65,6 +65,11 @@
         "http://*/*",
         "https://*/*"
     ],
+    "applications": {
+        "gecko": {
+            "id": "{531906d3-e22f-4a6c-a102-8057b88a1a63}"
+        }
+    },
     "incognito": "spanning",
     "manifest_version": 2
 }