Examine source code of HeadersSaver

{
  "manifest_version": 2,
  "name": "HeadersSaver",
  "author": "Anastasiia Chorna",
  "version": "1.0",
  "description": "Saving all request headers to session storage.",
  "background": {
    "scripts": [
      "header_saver.js"
    ]
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "tabs",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{215c6f45-0998-4735-9447-71edc9cd8b8c}"
    }
  }
}