Examine source code of Refererer

{
  "manifest_version": 2,
  "name": "Refererer",
  "version": "1.0",
  "description": "Displays HTTP Referer headers for all websites in a sidebar",
  "permissions": [
    "activeTab",
    "webRequest",
    "webRequestBlocking",
    "storage",
    "<all_urls>"
  ],
  "sidebar_action": {
    "default_panel": "sidebar.html",
    "default_title": "Refererer"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a74f420b-6aa5-4e47-aed5-4ab36c809c88}"
    }
  }
}