Examine source code of jk scroll

{
  "name": "jk scroll",
  "description": "Scroll with j and k",
  "manifest_version": 2,
  "version": "1.24",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-script.js"
      ],
      "run_at": "document_start"
    }
  ],
  "background": {
    "scripts": [
      "background-script.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "jkscroll@h43z",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "activeTab",
    "sessions"
  ]
}