Examine source code of Agent Spoof

{
  "manifest_version": 2,
  "name": "UA Bridge & Spoof",
  "version": "2.0",
  "icons": {
    "256": "icons/icon-256.png"
  },
  "description": "Spoofs HTTP Headers and sets cookie for Tampermonkey",
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "storage",
    "cookies",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{a1b2c3d4-e5f6-4a7b-9c10-123456789abc}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}