Examine source code of proxy-checker-vv1

{
  "manifest_version": 2,
  "name": "UA Header Spoofer",
  "version": "1.0",
  "description": "Spoof User-Agent via HTTP header",
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "data-ebah@gmail.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}