add firefox extension id (for auto distribution)

Author: medyo

public/manifest.json

@@ -16,5 +16,10 @@
     "48": "/logos/logo48.png",
     "128": "/logos/logo128.png"
   },
-  "content_security_policy": "script-src 'self' https://*.carbonads.com https://*.buysellads.net https://*.buysellads.com https://*.servedby-buysellads.com https://*.carbonads.net sha256-9wgUeE7o26PX9BlGznRgR+gJarj/ugHxm3UOzKP13EE='; object-src 'self'"
-}
+  "content_security_policy": "script-src 'self' https://*.carbonads.com https://*.buysellads.net https://*.buysellads.com https://*.servedby-buysellads.com https://*.carbonads.net sha256-9wgUeE7o26PX9BlGznRgR+gJarj/ugHxm3UOzKP13EE='; object-src 'self'",
+  "applications": {
+    "gecko": {
+      "id": "{f8793186-e9da-4332-aa1e-dc3d9f7bb04c}"
+    }
+  }
+}