Examine source code of To_do_korosan

{
  "manifest_version": 2,
  "name": "To_do_korosan",
  "version": "1.11",
  "description": "Change a background image of Trello.",
  "icons": {
    "48": "image/icon-48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.trello.com/*"
      ],
      "js": [
        "access.js"
      ]
    }
  ],
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "storage"
  ],
  "applications": {
    "gecko": {
      "id": "addon@to_do_koro.com"
    }
  },
  "browser_action": {
    "default_icon": {
      "19": "image/icon-19.png",
      "38": "image/icon-38.png"
    }
  }
}