Examine source code of ^^URL

{
  "manifest_version": 2,
  "name": "^^URL",
  "version": "7.18",
  "description": "Open the next numerical webpage.",
  "permissions": [
    "contextMenus",
    "tabs"
  ],
  "background": {
    "scripts": [
      "bg.js"
    ]
  },
  "icons": {
    "16": "icons/16.png",
    "48": "icons/48.png",
    "96": "icons/96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{db22bf9b-23a6-4a8c-9163-8fd853d9f170}"
    }
  }
}